16 years ago, When I had this class in College I DID think OpAmps appeared to generate power out of nothing (after seeing a dozen OpAmp circuits ommiting the external power supply it's easy to forget them), and I remember not being the only one of my classmates confused, so I appreciate the comment near the end!
I think because of labels like gain and amplifier we got this wrong idea. I have only recently come to the conclusion that the device is not the amplifier but that amplifier is something you make using the device. Even that could be wrong.
I think of it more like a flood gate on a dam, a little signal can let go to the full flow, except you've got a channel back to the floodgate to close it back up a bit. (I learned plumbing and electrics more or less at the same time, I'm always falling back on water analogies,lol)
The thing that finally got me to understand OpAmps was this: In a normal circuit, if two nodes are connected with nothing between them they have the same voltage and current can flow freely between them. OpAmps "break" that rule. The two inputs are a pseudo-node where the voltages are the same, BUT no current flows. If you introduce that into the math of circuits you get a really powerful tool that lets you do all of the things described here.
When I learned and found about the op amps, how they work, as this component was the solution to my problem I was having at that time, this thing opened up a huge window in my tiny hobbyist electronic world. In the beginning it almost feel like magic. You can make so many things after you understand this component. You finally start to understand the whole picture, how things work in the electronic world.
Oh boy the infamous 741, haha. You can't imagine the headaches that this little guy gave me in EE. Almost all of my PCB's that had the 741 never worked properly, and my professores would say "Oh the Schematic is correct and the theory is ok, but the 741 does not work for this application". It is a very simple op amp for sure. Amazing video!
About a year ago, I was at Dave Fullagar's home, the inventer of the uA741, the first internally compensated operational amplifier. He's as humble and sharp as ever. I actually met him after he retired from Maxim Integrated Products (one of three original founders), where I worked for a couple of years. Interestingly, he was supposed to be a geotechnical engineer but changed while at the university.
Is it possible that your circuits would have worked with an op-amp that had rail-to-rail outputs, which some do but the 741 does not necessarily? You can get differences between nominally equivalent op-amps with the same type number but of different makes. I designed a circuit for lithium cell management that worked well with a TLC272 op-amp made by Texas Instruments but it malfunctioned with a TLC272 made by ST Microelectronics. It turned out that the Texas Instruments TLC272 has rail-to-rail outputs although they are not demanded by the component specification (but not forbidden either), and the STM TLC272 does not have rail-to-rail outputs although it does conform to the published specification.
My OpAmp story: LM358 is a super-common, low cost OpAmp that is absolutely abysmal as an audio amplifier. It's fine for some purposes, but not that one. On three occasions I have needed to build an audio amplifier circuit and LM358 was the only OpAmp I had in my drawer. After much circuit fiddling, datasheet reading, and internet searching, I've managed to build an LM358 based audio amplifier circuit that was "better than nothing." That was the best I have managed. One trip to eBay and three weeks later, 100 cheap (around 10 cents a piece, after shipping) TDA2822M OpAmps arrived from China. I'll never use LM358 for audio again.
Great to the point video, clean slides, a lot of information per time! However, there are two mistakes in the differential amp slide (around 6:20); 1) The two inputs are interchanged. For non saturated operation (i.e. no comparator) the feedback path must always be closed, i.e., inverting input must be connected in any way to the output, 2) The two inputs must not be tied together. As you explain, the opamp amplifies the voltage difference between both inputs and does everything at its output to keep the voltage difference at the inputs as small as possible. So, a short circuit between the inputs makes it impossible for the opamp to work. Keep on with your good work!
I love to build things with OP-AMPs. Once I built my own PWM dimmer/speed controller consisting of a NE555, a UA741, a BUZ11 MOSFET, 7 resistors, 4 capacitors and a potentiometer. I operate my self-made 12V LED light strips on this dimmer. I simply used cable ducts for the LED strips. I drilled holes for 5mm LEDs in the cable duct cover. On the inside of the cover I soldered the wiring strands and the corresponding LED series resistors. In the stairwell I also have the same cable ducts with built-in LEDs just above the steps, which are switched using a self-made time switch with an OP-AMP and MOSFET. The time switch is controlled by a radar motion detector, which can also detect movements through walls. Advantage of the radar motion detector: It reacts to everything that moves, as long as it is not too small. But moving a finger is enough... PIR motion detectors only react to objects that are warmer than the ambient temperature.
Thankyou so much for the detailed and concise explaining! After 3 hours of binge searching for proper info on op-amp deployment and the various typical uses, Ive finnaly found your video and can now get to work on my project.
Very fast,short,brief introduction to OpAmp .For three years since 2017 , I never use/touch/fritzing/multisim-experiance in electronics. I stopped washhands reading electronics, many people started to use VR/AR/MR/XR to designed/demo the digital-electronics new technology ( Printed Electronics, small-palm-size FPGA ,XILINS/INTEL ,software-hardware programming beyond Arduino,Rasberry PI-4 . Suddenly a young lady replacing a young man in element 14 ? A new fresh starts .Good to see new face ! Karen keep it up .
Holy thank you for explaining it this way, no other relatively short video explains where the voltage goes to depending on the input, just that it amplifies one signal or flips another.
Hi, thanks for this video it's really good, one think on differential amplifier at 6:20 in the video, the positive and negative inputs look shorted and they should not be. thanks.
Question here: @3:45 you mentioned that an op amp can turn a sinusoidal ac wave to a square DC wave.. would the square wave not also be alternating between a positive and negative voltage making it not DC and still AC. Genuinely confussled, any responses help.
Question: At 6:13, should the positive and negative connection be wired together????? i'm not the greatest at this, but something doesn't seem right..... A quick google image search, and I see no schematic similar to that wiring...... am i wrong??
I think there is a small error at 6:22 where you short the 2 op-amp terminals together. Also, it should be negative feedback for operation stability; therefore, the formula signs change. Your concept is clear and instructional. It is helpful. Thanks.
At 6:22 Swap the + and - OpAmp inputs to the resistor network. Remove the wire connecting R₁ to R₂. Also: R₁ = R₂ and R₃ = R₄. Now the equation applies.
Well if you wanna go deep, there is a book(more like a short pdf) "op amps everyone" by texas instruments which explains about some applications of op amp as Audio,Video,Instrumentaion amplifiers
A good overview. Showing the components, pin callouts per component, and the overall circuits are helpful for context that many presentations lack. A lot of ground was covered going thorough different types without getting too bogged down.
Very nice introduction, 7:22 the inverting and non inverting inputs are mentioned the other way, should be non inverting to the capacitor and the resistor and the inverting to the voltage divider
Forgive me if I am wrong, but the schematic of the differential amplifier (6:18) does not make sense to me. Why would the two inputs be shortened essentially equalizing the potential on both + and -? In such a way, the output should be zero. I am looking to create an audio balanced to unbalanced converter, which should work as a differential amplifier, and cannot imagine that the two signals should be combined into a one.
So far "changing AC to DC" in my text books has always been shown as cutting off the lower or higher parts of the sine wave, could someone explain why a square wave, that looks as if it has both polarities is "DC"? 3:34
If the square wave is referenced to ground, it is a form of "pulsing DC" kind of like rectifier output. AC means the current is continually changing direction, but a pulsing on/off square wave signal could be averaged as a DC voltage. I don't know if the graph shown in the video is correct. If the square wave went from positive to negative, I would consider that a form of AC voltage.
Wow.... what a blast from my electronics technician days past!! I was an electronics tech in the 80s. Sometimes I really miss the days of troubleshooting circuits with a DMM and/or a scope. Fun times!!
Thank you for actually explaining the _mechanisms_ as well as elaborating a bit on the basic terms :) Most videos just show some footage and throw formulas in your face, it feels like those are made for people who already know the material.
Pause at 6:22. Is there a typo in this circuit? The 2 input signals are shorted. There is no way the amplifier is able to amplify if both inputs are always going to be equal because they are shorted together.
Thanks for this great introduction to op amps. As a newbie with limited experience, I don't see how the circuit at 6:13 can work -- the inverting and non-inverting inputs are connected together. Should this connection be removed, or replaced with a resistor? Thanks.
You are correct. There should not be a connection there. Also, if R3 is the feedback resistor, then it should be going to the inverting input. The circuit equation is also incorrect (note R2 and R4 don't show up in the equation! Also, the signs of Vin1 and Vin2 are going to be wrong). The circuit should more properly called a difference circuit - not differential. A differential amplifier is a term used for an entirely different beast. The correct equation should be Vout=-R3/R1*Vin1+(R1+R3)/R1*R4/(R2+R4)*Vin2. The difficulty will be getting R3 and (R1+R3)*R4/(R2+R4) to match (in order to get a good subtraction).
Karen, THANK YOU! I'm looking at a RADAR imaging circuit ala Gregory Charvat, and he is using on Quad Op amp chip in a couple of different ways. Your video helped me understand first was a simple amplifier, then an Active Low Pass Filter. SUPER helpful video! I learn so much watching you.
Karen, I am a retired auto tech building a 1967 Chevy pickup for myself. Using the “Op Amp” for a low fuel lamp. Now, with 0 ohms = Empty and 90 ohms = Full. Using this variable input into the inverting input could be used for turning on an LED. To set the point of this “On” signal for the LED, the non-inverting side can be the sweep of an 100 ohm potentiometer connected to B+, the sweep connected to the non-inverting (-) and adjusted for a resistance inside the fuel tank to 2 gallons, 3 gallons or whatever a guy/gal wants for a warning reserve. Using a 470 ohm resistor to an LED fixture marked low fuel would not effect the gauge, tank sender or the circuit. I am just bringing my project into the 21 century so my wife or son could drive safely but with reliability. After 40 years, I have found that is you over build a component and add it into a service manual, will last way longer. As a guy who would build an automatic to handle 600 HP, but only have 400 HP driving it. Properly cooled, it would last 30 years, instead of 10. On my idea of using an “Op Amp” in this fashion, would or should this work and be reliable? (LM358, 100 ohm pot, soldered terminals with shrink wrap and dielectric grease) ASE Master Tech since 1978! Thanks.
Yes but if you had a rectifier involved then if it could flatten out that wave for some potentially better used signal but you might still need a cap to smooth out the power differential since I imagine the current will be oscillating in response.
[6:17] non -invert connected directly to invert,that would be 0 volt difference I do not get at all. Is it the difference between the + and - supply which generates output? The connection between invert and non-invert should be broken and a separate resistor call it R5 should go to 0 volt from the non-invert and R2 R4 go to invert. I have a plug-in breadboard I will try it.
Yup! It went to the next slide and then I go wait that didn't look right, lol -- the connection between the non inverting and inverting inputs just need to be erased -- so R1 still connects to R3 and R2 still connects to R4, but the connection between those two nodes just needs erased :-) So you could just save that picture and erase that little line and be good to go with a nice basic diagram for a differential amplifier :-)
good vid! As you noted-They are very sensitive…and amp projects taught me that discreet component values are almost never exactly as rated…lol. I really didn’t understand them until i set up a dual rail power supply…and then it all “clicked”…to this day-i test every component for actual value…
Thanks for this video! I learned a lot from it! But I was confused at 6:55 you say "by swapping the resistor at the input with the feedback resistor". Should it be "by swapping the resistor at the input with the feedback capacitor"? Or am I missing something? Thanks a lot for your help!
@@kwgm8578 Thank you for the response. It is hard to know what is correct when you are trying ot teach yourself. As far as I knew what shes aid could have been corrct and there was some point I didn't understand, so thank you again!
Could I use an op amp to create a Baxandall Audio Eq as part of an audio preamplifier? I’m not an audiophile but rather a tech minded musician whose primary instruments are electric guitar and bass guitar.
2:11 shouldn’t GND be 0V instead? You would generally use the power supply as the stable electron source, leaving the ground plane to shield EMF and optionally provide a sink for shorts.
Well a couple comments: First: I appreciate your efforts and in general think you did a very good job. Second: As the audience I am a retired theoretical mathematician that is venturing into op-amps because I want to construct an instrument-pickup pre-amp similar to a Mic pre~amp for the acoustic stringed instruments I've built in my retirement, thus I am without what many who pursue electronics have derived as being the case or required without needing to be indicated. Therefore, I suggest, please make it clear in the presentation the two following conclusions and one extra conceot I have derived thru experimentation and have indicated in 1 thru 3 seen below. 1: When you say Voltage at the (+) input is greater than the Voltage at the (-) input I think it should be indicated that Sign indicating polarity matters for the order relation of greater, equal to, or less than. eg, (-6 volts) is less than (+6 volts), they are not equal. 2: The (+ input), (- input) difference that is multiplied by the gain=M, idiosyncratic to the device, should probably be indicated as being the result of the absolute value of [(volt at + input) - (volt at -input)], not the difference of V-, V+ without absolute value being indicated because it can make a difference that is not intended. & Regardless of which input receives the signal, where this is either the (- input) or the (+ input), for any given instance of the output Voltage when the Vdiff is below the saturation threshold we have Vout, in magnitude without sign, equals M times the absolute value of Vdiff. & (if Vdiff equals or is above the saturation limit Vout is either equal to the Voltage at one of the rails in a Dual Supply scheme, or at O volts or Vcc in a Single supply scheme) & This Vout has a Sign or polarity of (-) if and only if the Voltage at the (- input) is greater than the Voltage at the (+ input), & This Vout has a Sign or polarity of (+) if and only if the Voltage at the (+ input) is greater than Voltage at the (- input), & The Sign or polarity is in part dependent on what establishes ground where this can be in the case of a Single supply system what is commonly thought of as where the (-) terminal of the supply attaches and often though of as O volts. or It can be the floating or virtual ground established in a Dual Power supply where it has a value of Zero much like Zero found on the subset or partition of the Real number line called the interval of [-5 to +5]. 3: I also think the Dual Supply scheme should be explained where it can be easily thought of as two batteries in series where the (+) end of one battery provides V+, & the (-) end of the other battery provides V-, & the ground or floating ground or what ever the reference point is called that consists of where the two batteries actually connect to each other in the Dual scheme is the ground being referred to. (I see this as important because many diagrams for simple non-inverting amplification of the signal are actually meant for the Dual Supply scheme & likely will otherwise match every part of the signal input to Zero volts at Vout if a Single power supply is used with the (-) terminal of the battery acting as ground & with a resistor to ground in a voltage divider connected on its plus side to the (- input) pin as I found out by not realizing the Dual scheme was required and it was a bit of a bitch to figure out why it was not working as advertised. Aside from what I suggested being added, you gals and guys did good and I think my adds would just inch it to, did a really great or fabulous job. Thanks again for the video....
At 6:22 Swap the + and - OpAmp inputs to the resistor network. Remove the wire connecting R₁ to R₂. Also: R₁ = R₂ and R₃ = R₄. Now the equation applies.
For the differentiator you are swapping the feedback capacitor with the input resistor (not the resistor at the input with feedback resistor as narrated). The image shown is correct though. Awesome video thank you.
This is a fair explanation for someone who already understands op amps. I wish it was directed more toward beginners. Example: You show AC sine wave voltage to the + pin and a square wave at the output. It would have been so easy to show an actual (or animated) oscilloscope trace showing the input crossing 0 volts and the output changing polarity. Single power supply only makes it more difficult to understand. The unity gain buffer is also difficult to understand as you don't explain that the output is essentially trying to drive the -pin to equal the +pin. I couldn't get any further.
Nice overview Karen, thanks! One note, I THINK you reversed the resistor-capacitor and voltage divider attachment points (inverting vs. non-inverting) when you described the astable multivibrator circuit at ~7:25.
At 7:25, swap the OpAmp inputs in the diagram to get the astable multivibrator. The circuit needs positive feedback to slew rapidly and negative feedback to delay the flip to the opposite polarity.
Hey, this was a well done video and a great presenter as well! No droning on about unless info and directly to the point. And, several schematics of uses of op-amps and what they are used for. This was great! Thanks!!
Thanks for the video, that helps me undferstand the bits I wasn't sure about. One question, what are all those posters in the background? They look like they could be helpful for identifying components and the like. If they are, where can we buy them?
Thank you so much for this video! The explanation right at 3:17 finally got it to click in my brain why people use these as buffers, even after years of explanations that felt like they were avoiding the question.
This is a great video, but just like dozens of others there is no real world applications that they are referenced to otherwise it's the same old description. The first one who does a video that shows the multiple applications of op-amps how they're used in the circuit what in the circuit is used to control it and what hardware outside the circuit is ithe nput and output from the op amp wins the prize. All op amp videos I have seen begin beyond the beginner stage and many are lost in what their real world applications are. 8:45
I have an electric guitar, it has active pickups. I looked at the schematic for the EMG 81, it runs a high pass RC filter feeding into a feedback op-amp. I can't find a schematic for the EMG 85 Neck Pickup, but it sounds much warmer than the bridge pickup, so the EMG 85 must have a low pass filter and a feedback op-amp.
When I was in the Navy I worked on a machine that had hundreds of individual circuits, each tuned to create a different analog symbol on a display screen. All of them used an op amp to shape the circuit to make things like plane, subs, boats, numbers, everything you can imagine. But instead of drawing them digitally like nowadays, the Navy used thousands of op amps instead.
At 6:20, that "differential" amplifier is not even close. First, the opamp's inputs are shorted together so you will see only its drift/common mode at the output. Second, the inverting and non-inverting inputs are backwards; the feedback must excite the inverting input for negative feedback. Third, the output equation is wrong. If you flip the opamp, remove the shorting segment, and make R4=R3 and R2=R1, then the output will be Vout=R3/R1(V2-V1) within the opamp's specifications and power supplies. At 7:10, integrators are LOW pass filters and the circuit you show is an integrator; the capacitor integrates the charge flowing through R3. The sin(.) at the input should become - Acos(.) at the output. At 7:20 and 7:40, your opamps need flipped once again, but that one-shot won't work anyway -- your trigger MUST zero the capacitor's charge first.
oh my, i feel like i have been hit over the head with a shovel. I think i need to watch this over again about another 100 times, first time round i'm sure my brain thought it was in Japanese, oh i'm getting old :o)
It's a bit like being in a lecture where you are totally new to the subject and the teacher has no memory or comprehension of what it's like not to understand what it is she is teaching. The hit over the head with a shovel analogy is spot on. Thankfully there are much better teachers out there.
@ggg666 >True that! I am just a retired auto tech. I figured an app Amp is used to make a “Low Fuel” lamp controller. I would have watch this a lot to get my brain around it. ASE Master Tech since 1978
Wow, clean pictures, again! This is good stuff to know and apply. I'm going to have to go over your previous videos to break it down for the old guy. It almost makes sense. Be right back!
Great overview Karen!! One of the more versatile and useful devices in your circuit arsenal. There are some great OP AMP cookbooks out there from classic authors like Forrest Mims III.
You left out the API 2520 footprint and Neumann edge pin footprint.But then I am only familiar with those because I built some 500 series kits with 2520 style op amps in them. A few compressors, EQs and mic pres. But those op amp footprints date back to the origin of op amps in pre IC computing. The API 2520 and similar came a little bit before IC op amps came into being if I remember correctly. So they are through hole op amps. With actual discrete parts that have to be soldered in to place. Pretty challenging to get 30-40 solder joints just right with no bridge on a PCB the size of a postage stamp.
Karen, I think one of the more interesting op-amp circuits is simulating a large inductance with a gyrator configuration. Actual large inductors are heavy and bulky but a two port op-amp gyrator is only a few small components, making the circuit very compact. It's a convenient way to produce an inductance in the Henrys.
Your thumbnail shows V1 > V2 with the output at the negative rail Way to go to confuse folks. And you have the inputs reversed again at 7:25 on the astable multivibrator.
3:47 "DC" Square wave? How is the square wave DC if the current is alternating at the same frequency as the input? If the square wave is alternating at an extremely lower frequency that it's almost constant, then I would say, that's DC.
Comparitor can be used as a smart lithium charger as well. Im trying to figure out how to trick a smart charger to just feed all it's power on high and im SO CLOSE. Zeroing in in this component and i just need to now what to just where and put a switch on it.
I have been researching DIY guitar pedals lately. I noticed some of them use one op amp 2 amplify the signal, and a second one to invert the signal. But the most fun I have is replacing the diodes with different versions like germanium or LED. I'm still trying to figure out why they want to invert the signal after they amplify?
Thanks a lot. Just one mistake I think. 6:20 the inverting and non-inverting inputs have been connected, making it a single node. Voltage difference is always zero.
can you give more specifics on creating a voltage divider using resistors (mentioned @1:30)? just following the schematic at that part at the video "creates a voltage divider"? Man. why did i just buy and build two power dual output power supply kits from jameco (besides the fact that they'll come in handy at some point and jameco is awesome)
The best thing about OpAmps is they neither affect the previous circuit (high impedance) or the next circuit (low impedance). And you can control the output impedance by putting a series resistor, do whenever the output load is 0 ohms your impedance in the output will always be what you defined in the series resistor.
Thanks Kare, it is a nice lesson. So much to still discuss on opamps. I like them very much, IMHO they facilitate the design and implementation in a lot of projects.
I learned "virtual ground" is a big aspect to op-amps. I never fully grasped the concept to my satisfaction, but the way I understand it is the current between the two inputs is so small a virtual ground potential is present between them. That is if one of the inputs, either the inverting or non-inverting, is pinned to ground. Can anyone offer more on this? It's a great video, and I would have loved to have it as a learning resource back in the day.
You understood it wrong. There is no such thing as a 'virtual ground potential'. In an inverting configuration, the non-inverting input is grounded and the inverting input presents a virtual ground because the opamp works to keep the voltages at both inputs the same. In this mode the opamp is sensing input current rather than voltage, as the voltage is always zero. That's why it is a virtual ground.
Interested in OpAmps? Check out this fresh content from Derek's on the topic here: th-cam.com/video/kF1wGW-h4Y8/w-d-xo.html
16 years ago, When I had this class in College I DID think OpAmps appeared to generate power out of nothing (after seeing a dozen OpAmp circuits ommiting the external power supply it's easy to forget them), and I remember not being the only one of my classmates confused, so I appreciate the comment near the end!
I think because of labels like gain and amplifier we got this wrong idea. I have only recently come to the conclusion that the device is not the amplifier but that amplifier is something you make using the device. Even that could be wrong.
We must have had the same teacher :D
@@dukeatreidas9771 ikr?
I think of it more like a flood gate on a dam, a little signal can let go to the full flow, except you've got a channel back to the floodgate to close it back up a bit. (I learned plumbing and electrics more or less at the same time, I'm always falling back on water analogies,lol)
@@Telee_Pawt нет, это устройство именно усилитель !с очень большим коэфицентом усиления! Без обратной связи около миллиона!
I'm currently in a circuits class and this has got to be the best explanation of op amps I've ever seen. Thank you!
The thing that finally got me to understand OpAmps was this:
In a normal circuit, if two nodes are connected with nothing between them they have the same voltage and current can flow freely between them.
OpAmps "break" that rule. The two inputs are a pseudo-node where the voltages are the same, BUT no current flows. If you introduce that into the math of circuits you get a really powerful tool that lets you do all of the things described here.
she explained the subject in mins what my professor couldnt in 40 hrs of university classes
😂
Then surely he wasn't a professor at all. A simple water flow example is also useful for opamp explanation.
Thats why most of indian engineers are unemployed, because of poor way of delivering concept and below standard faculty
@@sujoypaul1874 don't lose hope bro
You can learn everything on the Internet
@@SumitSingh-iz9pw core subjects nhi milte bhai,bas dukan chalri h sabki
When I learned and found about the op amps, how they work, as this component was the solution to my problem I was having at that time, this thing opened up a huge window in my tiny hobbyist electronic world. In the beginning it almost feel like magic. You can make so many things after you understand this component. You finally start to understand the whole picture, how things work in the electronic world.
Oh boy the infamous 741, haha. You can't imagine the headaches that this little guy gave me in EE. Almost all of my PCB's that had the 741 never worked properly, and my professores would say "Oh the Schematic is correct and the theory is ok, but the 741 does not work for this application". It is a very simple op amp for sure. Amazing video!
Considering how much trouble the research for this episode gave me, I think I can imagine the headache. Haha. Glad you liked it!
About a year ago, I was at Dave Fullagar's home, the inventer of the uA741, the first internally compensated operational amplifier. He's as humble and sharp as ever. I actually met him after he retired from Maxim Integrated Products (one of three original founders), where I worked for a couple of years. Interestingly, he was supposed to be a geotechnical engineer but changed while at the university.
Is it possible that your circuits would have worked with an op-amp that had rail-to-rail outputs, which some do but the 741 does not necessarily? You can get differences between nominally equivalent op-amps with the same type number but of different makes. I designed a circuit for lithium cell management that worked well with a TLC272 op-amp made by Texas Instruments but it malfunctioned with a TLC272 made by ST Microelectronics. It turned out that the Texas Instruments TLC272 has rail-to-rail outputs although they are not demanded by the component specification (but not forbidden either), and the STM TLC272 does not have rail-to-rail outputs although it does conform to the published specification.
My OpAmp story: LM358 is a super-common, low cost OpAmp that is absolutely abysmal as an audio amplifier. It's fine for some purposes, but not that one. On three occasions I have needed to build an audio amplifier circuit and LM358 was the only OpAmp I had in my drawer. After much circuit fiddling, datasheet reading, and internet searching, I've managed to build an LM358 based audio amplifier circuit that was "better than nothing." That was the best I have managed. One trip to eBay and three weeks later, 100 cheap (around 10 cents a piece, after shipping) TDA2822M OpAmps arrived from China. I'll never use LM358 for audio again.
Great to the point video, clean slides, a lot of information per time! However, there are two mistakes in the differential amp slide (around 6:20);
1) The two inputs are interchanged. For non saturated operation (i.e. no comparator) the feedback path must always be closed, i.e., inverting input must be connected in any way to the output,
2) The two inputs must not be tied together. As you explain, the opamp amplifies the voltage difference between both inputs and does everything at its output to keep the voltage difference at the inputs as small as possible. So, a short circuit between the inputs makes it impossible for the opamp to work.
Keep on with your good work!
Thanks thought i was going to lose my mind.
@@openyoureyes7539 exactly same here. Just when you start thinking you understand smth, the teacher makes a mistake like that..
Good video. Had to watch for a class. I have never understood something less in my life.
thank you for actually making op amps make sense this is the best video ive ever watched on youtube :D
This was actually non-sense. Are you from Australia?
@@mrpeterfrazier 🤣👍
I love to build things with OP-AMPs. Once I built my own PWM dimmer/speed controller consisting of a NE555, a UA741, a BUZ11 MOSFET, 7 resistors, 4 capacitors and a potentiometer.
I operate my self-made 12V LED light strips on this dimmer. I simply used cable ducts for the LED strips. I drilled holes for 5mm LEDs in the cable duct cover. On the inside of the cover I soldered the wiring strands and the corresponding LED series resistors.
In the stairwell I also have the same cable ducts with built-in LEDs just above the steps, which are switched using a self-made time switch with an OP-AMP and MOSFET. The time switch is controlled by a radar motion detector, which can also detect movements through walls.
Advantage of the radar motion detector: It reacts to everything that moves, as long as it is not too small. But moving a finger is enough... PIR motion detectors only react to objects that are warmer than the ambient temperature.
Thankyou so much for the detailed and concise explaining!
After 3 hours of binge searching for proper info on op-amp deployment and the various typical uses, Ive finnaly found your video and can now get to work on my project.
Very fast,short,brief introduction to OpAmp .For three years since 2017 , I never use/touch/fritzing/multisim-experiance in electronics. I stopped washhands reading electronics, many people started to use VR/AR/MR/XR to designed/demo the digital-electronics new technology ( Printed Electronics, small-palm-size FPGA ,XILINS/INTEL ,software-hardware programming beyond Arduino,Rasberry PI-4 . Suddenly a young lady replacing a young man in element 14 ? A new fresh starts .Good to see new face ! Karen keep it up .
Holy thank you for explaining it this way, no other relatively short video explains where the voltage goes to depending on the input, just that it amplifies one signal or flips another.
Hands down, this is the best op-amp tutorial
Hi, thanks for this video it's really good, one think on differential amplifier at 6:20 in the video, the positive and negative inputs look shorted and they should not be. thanks.
You are right, the should not be shorted and they look like they are. Good catch
Yup, I just came to the comments to make sure that someone caught that already. Well played.
Question here: @3:45 you mentioned that an op amp can turn a sinusoidal ac wave to a square DC wave.. would the square wave not also be alternating between a positive and negative voltage making it not DC and still AC. Genuinely confussled, any responses help.
The best explanation of the basics of Op Amps I have ever seen...
Perfectly explained refresher of op-amps. Just what I needed. Thank you!
Probably the best explanation of op-amps I've seen so far. Thanks!
not quite
Question: At 6:13, should the positive and negative connection be wired together????? i'm not the greatest at this, but something doesn't seem right..... A quick google image search, and I see no schematic similar to that wiring...... am i wrong??
no, the inputs are shorted together...but i'm no expert, and you always think "am i missing something here ?"
They should not be connected.
en.m.wikipedia.org/wiki/File:Op-Amp_Differential_Amplifier.svg
You have a load on positive and negative and to ground so no problem
@@paxanellie regardless of any load, they are both at the same potential.
if the inputs are connected together, it's not gonna work..
I think there is a small error at 6:22 where you short the 2 op-amp terminals together. Also, it should be negative feedback for operation stability; therefore, the formula signs change.
Your concept is clear and instructional. It is helpful. Thanks.
At 6:22 Swap the + and - OpAmp inputs to the resistor network. Remove the wire connecting R₁ to R₂.
Also: R₁ = R₂ and R₃ = R₄.
Now the equation applies.
Really great, simple, clear, precise, going straight to the point. Thank you for this perfect video as we would like to see more often.
Hi Karen can you make a series of each opamp "use case" ? i never found an exhaustive list that explains in depth each case. Thx
^^ I second this
Rt
Well if you wanna go deep, there is a book(more like a short pdf) "op amps everyone" by texas instruments which explains about some applications of op amp as Audio,Video,Instrumentaion amplifiers
@@saimanojnelavelli5911 thanks
She is a karen
A good overview. Showing the components, pin callouts per component, and the overall circuits are helpful for context that many presentations lack. A lot of ground was covered going thorough different types without getting too bogged down.
Thank you for taking the time to explain op amps.
Very nice introduction, 7:22 the inverting and non inverting inputs are mentioned the other way, should be non inverting to the capacitor and the resistor and the inverting to the voltage divider
Brilliant Explanation. The whole OpAmp summed up in the best possible way !
I could follow along well until 5:28. So what is this R1 in addition for in contrast to the previous example?
Forgive me if I am wrong, but the schematic of the differential amplifier (6:18) does not make sense to me. Why would the two inputs be shortened essentially equalizing the potential on both + and -? In such a way, the output should be zero. I am looking to create an audio balanced to unbalanced converter, which should work as a differential amplifier, and cannot imagine that the two signals should be combined into a one.
So far "changing AC to DC" in my text books has always been shown as cutting off the lower or higher parts of the sine wave, could someone explain why a square wave, that looks as if it has both polarities is "DC"? 3:34
If the square wave is referenced to ground, it is a form of "pulsing DC" kind of like rectifier output. AC means the current is continually changing direction, but a pulsing on/off square wave signal could be averaged as a DC voltage. I don't know if the graph shown in the video is correct. If the square wave went from positive to negative, I would consider that a form of AC voltage.
Yes, a square wavevisn't really dc.
Wow.... what a blast from my electronics technician days past!! I was an electronics tech in the 80s. Sometimes I really miss the days of troubleshooting circuits with a DMM and/or a scope. Fun times!!
Thank you for actually explaining the _mechanisms_ as well as elaborating a bit on the basic terms :)
Most videos just show some footage and throw formulas in your face, it feels like those are made for people who already know the material.
Pause at 6:22. Is there a typo in this circuit? The 2 input signals are shorted. There is no way the amplifier is able to amplify if both inputs are always going to be equal because they are shorted together.
Thanks for this great introduction to op amps. As a newbie with limited experience, I don't see how the circuit at 6:13 can work -- the inverting and non-inverting inputs are connected together. Should this connection be removed, or replaced with a resistor? Thanks.
Your absolutely right, the inputs shouldn't be connected with each other.
You are correct. There should not be a connection there. Also, if R3 is the feedback resistor, then it should be going to the inverting input. The circuit equation is also incorrect (note R2 and R4 don't show up in the equation! Also, the signs of Vin1 and Vin2 are going to be wrong).
The circuit should more properly called a difference circuit - not differential. A differential amplifier is a term used for an entirely different beast.
The correct equation should be Vout=-R3/R1*Vin1+(R1+R3)/R1*R4/(R2+R4)*Vin2. The difficulty will be getting R3 and (R1+R3)*R4/(R2+R4) to match (in order to get a good subtraction).
Karen, THANK YOU! I'm looking at a RADAR imaging circuit ala Gregory Charvat, and he is using on Quad Op amp chip in a couple of different ways. Your video helped me understand first was a simple amplifier, then an Active Low Pass Filter. SUPER helpful video! I learn so much watching you.
Karen, I am a retired auto tech building a 1967 Chevy pickup for myself. Using the “Op Amp” for a low fuel lamp. Now, with 0 ohms = Empty and 90 ohms = Full. Using this variable input into the inverting input could be used for turning on an LED. To set the point of this “On” signal for the LED, the non-inverting side can be the sweep of an 100 ohm potentiometer connected to B+, the sweep connected to the non-inverting (-) and adjusted for a resistance inside the fuel tank to 2 gallons, 3 gallons or whatever a guy/gal wants for a warning reserve. Using a 470 ohm resistor to an LED fixture marked low fuel would not effect the gauge, tank sender or the circuit. I am just bringing my project into the 21 century so my wife or son could drive safely but with reliability. After 40 years, I have found that is you over build a component and add it into a service manual, will last way longer.
As a guy who would build an automatic to handle 600 HP, but only have 400 HP driving it. Properly cooled, it would last 30 years, instead of 10. On my idea of using an “Op Amp” in this fashion, would or should this work and be reliable? (LM358, 100 ohm pot, soldered terminals with shrink wrap and dielectric grease) ASE Master Tech since 1978! Thanks.
Perfectly explained of op-amps. Just what I needed. Thank you for Perfectly explained
@3:46 I would say that it's a sine wave to square wave converter rather than being an AC to DC converter..
Yes but if you had a rectifier involved then if it could flatten out that wave for some potentially better used signal but you might still need a cap to smooth out the power differential since I imagine the current will be oscillating in response.
@@Phantastischphilok, but it would be the bridge rectifier that was converting to dc in that case, not the op amp.
You Tube algorithm finally came through with something useful. Didn’t even need to hear the content to sub, Element 14 is awesome
[6:17] non -invert connected directly to invert,that would be 0 volt difference I do not get at all. Is it the difference between the + and - supply which generates output? The connection between invert and non-invert should be broken and a separate resistor call it R5 should go to 0 volt from the non-invert and R2 R4 go to invert. I have a plug-in breadboard I will try it.
Great vintage Oscilloscope in the back. Excellent for warming up your lunch while working.
Or as a mechanic you can warm up your lunch on a 350 cu. In. small block LS3 corvette engine
Your differential amplifier circuit has an error in it....there should be no connection at the R3/R1 to non inverting pin...
thank god, i am a beginner, so, i was totally wrecking my brain over how it could possible work...
Yup! It went to the next slide and then I go wait that didn't look right, lol -- the connection between the non inverting and inverting inputs just need to be erased -- so R1 still connects to R3 and R2 still connects to R4, but the connection between those two nodes just needs erased :-)
So you could just save that picture and erase that little line and be good to go with a nice basic diagram for a differential amplifier :-)
good vid! As you noted-They are very sensitive…and amp projects taught me that discreet component values are almost never exactly as rated…lol. I really didn’t understand them until i set up a dual rail power supply…and then it all “clicked”…to this day-i test every component for actual value…
one can not be greatful enough that someone like you explains things so that they are very easy to understand.
A very good video.
Thanks for this video! I learned a lot from it! But I was confused at 6:55 you say "by swapping the resistor at the input with the feedback resistor". Should it be "by swapping the resistor at the input with the feedback capacitor"? Or am I missing something? Thanks a lot for your help!
Yes, you're correct, she misspoke. Regardless, the circuit is right.
@@kwgm8578 Thank you for the response. It is hard to know what is correct when you are trying ot teach yourself. As far as I knew what shes aid could have been corrct and there was some point I didn't understand, so thank you again!
Could I use an op amp to create a Baxandall Audio Eq as part of an audio preamplifier?
I’m not an audiophile but rather a tech minded musician whose primary instruments are electric guitar and bass guitar.
6:22 is that a mistake that the + - are short circuited?
2:11 shouldn’t GND be 0V instead? You would generally use the power supply as the stable electron source, leaving the ground plane to shield EMF and optionally provide a sink for shorts.
Well a couple comments:
First: I appreciate your efforts and in general think you did a very good job.
Second: As the audience I am a retired theoretical mathematician that is venturing into op-amps because I want to construct an instrument-pickup pre-amp similar to a Mic pre~amp for the acoustic stringed instruments I've built in my retirement, thus I am without what many who pursue electronics have derived as being the case or required without needing to be indicated.
Therefore, I suggest, please make it clear in the presentation the two following conclusions and one extra conceot I have derived thru experimentation and have indicated in 1 thru 3 seen below.
1: When you say Voltage at the (+) input is greater than the Voltage at the (-) input I think it should be indicated that Sign indicating polarity matters for the order relation of greater, equal to, or less than. eg, (-6 volts) is less than (+6 volts), they are not equal.
2: The (+ input), (- input) difference that is multiplied by the gain=M, idiosyncratic to the device, should probably be indicated as being the result of the absolute value of [(volt at + input) - (volt at -input)], not the difference of V-, V+ without absolute value being indicated because it can make a difference that is not intended.
&
Regardless of which input receives the signal, where this is either the (- input) or the (+ input),
for any given instance of the output Voltage when the Vdiff is below the saturation threshold we have Vout, in magnitude without sign, equals M times the absolute value of Vdiff. & (if Vdiff equals or is above the saturation limit Vout is either equal to the Voltage at one of the rails in a Dual Supply scheme, or at O volts or Vcc in a Single supply scheme)
&
This Vout has a Sign or polarity of (-) if and only if the Voltage at the (- input) is greater than the Voltage at the (+ input),
&
This Vout has a Sign or polarity of (+) if and only if the Voltage at the (+ input) is greater than Voltage at the (- input),
&
The Sign or polarity is in part dependent on what establishes ground where this can be in the case of a Single supply system what is commonly thought of as where the (-) terminal of the supply attaches and often though of as O volts.
or
It can be the floating or virtual ground established in a Dual Power supply where it has a value of Zero much like Zero found on the subset or partition of the Real number line called the interval of [-5 to +5].
3: I also think the Dual Supply scheme should be explained where it can be easily thought of as two batteries in series where the (+) end of one battery provides V+, & the (-) end of the other battery provides V-, & the ground or floating ground or what ever the reference point is called that consists of where the two batteries actually connect to each other in the Dual scheme is the ground being referred to. (I see this as important because many diagrams for simple non-inverting amplification of the signal are actually meant for the Dual Supply scheme & likely will otherwise match every part of the signal input to Zero volts at Vout if a Single power supply is used with the (-) terminal of the battery acting as ground & with a resistor to ground in a voltage divider connected on its plus side to the (- input) pin as I found out by not realizing the Dual scheme was required and it was a bit of a bitch to figure out why it was not working as advertised.
Aside from what I suggested being added, you gals and guys did good and I think my adds would just inch it to, did a really great or fabulous job.
Thanks again for the video....
There's a short circuit between the inputs on 6:12 (differential amplifier).
Yup. Someone forgot to check this one.
At 6:22 Swap the + and - OpAmp inputs to the resistor network. Remove the wire connecting R₁ to R₂.
Also: R₁ = R₂ and R₃ = R₄.
Now the equation applies.
For the differentiator you are swapping the feedback capacitor with the input resistor (not the resistor at the input with feedback resistor as narrated). The image shown is correct though. Awesome video thank you.
Hi, on the "Differential" circuit, why is it that the inverting and non-inverting terminal of the op amp are shorted ?
I think that is a mistake in the diagram - well spotted!
This is a fair explanation for someone who already understands op amps. I wish it was directed more toward beginners. Example: You show AC sine wave voltage to the + pin and a square wave at the output. It would have been so easy to show an actual (or animated) oscilloscope trace showing the input crossing 0 volts and the output changing polarity. Single power supply only makes it more difficult to understand. The unity gain buffer is also difficult to understand as you don't explain that the output is essentially trying to drive the -pin to equal the +pin. I couldn't get any further.
This is the best video I've ever seen for op-amps srsly
What would be a good application for an op-amp in the buffer configuration?
Nice overview Karen, thanks! One note, I THINK you reversed the resistor-capacitor and voltage divider attachment points (inverting vs. non-inverting) when you described the astable multivibrator circuit at ~7:25.
Dino Papas who.. what?
At 7:25, swap the OpAmp inputs in the diagram to get the astable multivibrator. The circuit needs positive feedback to slew rapidly and negative feedback to delay the flip to the opposite polarity.
Hi there, nice video ! can you explain how op amps (lm393) are used as over voltage protection in ATX power supplies. Thanks.
Hey, this was a well done video and a great presenter as well! No droning on about unless info and directly to the point. And, several schematics of uses of op-amps and what they are used for. This was great! Thanks!!
Thanks for the video, that helps me undferstand the bits I wasn't sure about. One question, what are all those posters in the background? They look like they could be helpful for identifying components and the like. If they are, where can we buy them?
I got a lot of them from TinkrPostr. You should be able to buy them there.
Great video, it made so much EE come rushing back into my brain.
Great lecture Karen . But I guess I will have to attend this lecture a few times more . Subscribed 😀
Thank you so much for this video! The explanation right at 3:17 finally got it to click in my brain why people use these as buffers, even after years of explanations that felt like they were avoiding the question.
Great to hear!
If you put a potentiometer in replace of the resistor, would that be able to control the gain of the op amp?
Great video. Any hobby/tech level book recommendations that go deeper into op-amps? It’s one area I’ve always had trouble wrapping my head around.
Searching for "Forrest M. Mims" + Op amp will unearth a goldmine
The Art of Electronics - Paul Horowitz
@@bryansiepert9222 what's the title of the book?
This is a great video, but just like dozens of others there is no real world applications that they are referenced to otherwise it's the same old description. The first one who does a video that shows the multiple applications of op-amps how they're used in the circuit what in the circuit is used to control it and what hardware outside the circuit is ithe nput and output from the op amp wins the prize. All op amp videos I have seen begin beyond the beginner stage and many are lost in what their real world applications are. 8:45
So far the best basic Op-Amps explanation in youtube.
Thanks very much indeed. I would like to know about the role of Op-amps in fast transient Low Dropout Regulator Circuit.
I have an electric guitar, it has active pickups. I looked at the schematic for the EMG 81, it runs a high pass RC filter feeding into a feedback op-amp. I can't find a schematic for the EMG 85 Neck Pickup, but it sounds much warmer than the bridge pickup, so the EMG 85 must have a low pass filter and a feedback op-amp.
When I was in the Navy I worked on a machine that had hundreds of individual circuits, each tuned to create a different analog symbol on a display screen. All of them used an op amp to shape the circuit to make things like plane, subs, boats, numbers, everything you can imagine. But instead of drawing them digitally like nowadays, the Navy used thousands of op amps instead.
Thank you sssooooo much!!
As a woman engineer, I felt sooo empowered to see you explaining. Keep the good work going 👏
At 6:20, that "differential" amplifier is not even close. First, the opamp's inputs are shorted together so you will see only its drift/common mode at the output. Second, the inverting and non-inverting inputs are backwards; the feedback must excite the inverting input for negative feedback. Third, the output equation is wrong. If you flip the opamp, remove the shorting segment, and make R4=R3 and R2=R1, then the output will be Vout=R3/R1(V2-V1) within the opamp's specifications and power supplies.
At 7:10, integrators are LOW pass filters and the circuit you show is an integrator; the capacitor integrates the charge flowing through R3. The sin(.) at the input should become - Acos(.) at the output. At 7:20 and 7:40, your opamps need flipped once again, but that one-shot won't work anyway -- your trigger MUST zero the capacitor's charge first.
oh my, i feel like i have been hit over the head with a shovel. I think i need to watch this over again about another 100 times,
first time round i'm sure my brain thought it was in Japanese, oh i'm getting old :o)
I only watched it once, but paused it about 30 times!
It's a bit like being in a lecture where you are totally new to the subject and the teacher has no memory or comprehension of what it's like not to understand what it is she is teaching. The hit over the head with a shovel analogy is spot on. Thankfully there are much better teachers out there.
I had to learn these from a book. Enjoy!
@@WistrelChianti Some people learn differently. I found this to be the most concise and informative explanations I've found so far after a few videos.
@ggg666 >True that! I am just a retired auto tech. I figured an app Amp is used to make a “Low Fuel” lamp controller.
I would have watch this a lot to get my brain around it.
ASE Master Tech since 1978
Wow, clean pictures, again! This is good stuff to know and apply.
I'm going to have to go over your previous videos to break it down for the old guy. It almost makes sense. Be right back!
Thanks! I've been making my own graphics for a while now. I hope they help make the information easier to understand.
Wow! Thank you Karen. This is the best description of op-amps I've seen.
Great overview Karen!! One of the more versatile and useful devices in your circuit arsenal. There are some great OP AMP cookbooks out there from classic authors like Forrest Mims III.
That is the quintessential bible for opamp circuits.
Watching from São Paulo , Brazil. Thanks Karen! :D
A little error...
Employ positive feedback from output to +input(noninverting) by means of resistor(not named in this diagram).
a little...
You left out the API 2520 footprint and Neumann edge pin footprint.But then I am only familiar with those because I built some 500 series kits with 2520 style op amps in them.
A few compressors, EQs and mic pres.
But those op amp footprints date back to the origin of op amps in pre IC computing.
The API 2520 and similar came a little bit before IC op amps came into being if I remember correctly.
So they are through hole op amps. With actual discrete parts that have to be soldered in to place.
Pretty challenging to get 30-40 solder joints just right with no bridge on a PCB the size of a postage stamp.
God where was this video when i was taking circuit theory 4 years ago 😭😭 excellent work ty
Karen, I think one of the more interesting op-amp circuits is simulating a large inductance with a gyrator configuration. Actual large inductors are heavy and bulky but a two port op-amp gyrator is only a few small components, making the circuit very compact. It's a convenient way to produce an inductance in the Henrys.
So Opamps are just circuits with output voltage proportional to input voltage! Great video!!
at 7:27 what you said contradicts the circuit on the screen please correct this
Your thumbnail shows V1 > V2 with the output at the negative rail Way to go to confuse folks.
And you have the inputs reversed again at 7:25 on the astable multivibrator.
3:47 "DC" Square wave? How is the square wave DC if the current is alternating at the same frequency as the input? If the square wave is alternating at an extremely lower frequency that it's almost constant, then I would say, that's DC.
Comparitor can be used as a smart lithium charger as well.
Im trying to figure out how to trick a smart charger to just feed all it's power on high and im SO CLOSE. Zeroing in in this component and i just need to now what to just where and put a switch on it.
I would like to know if I can use an Op Amp to increase the value of the current from 1mA to 10mA.
I have been researching DIY guitar pedals lately. I noticed some of them use one op amp 2 amplify the signal, and a second one to invert the signal. But the most fun I have is replacing the diodes with different versions like germanium or LED. I'm still trying to figure out why they want to invert the signal after they amplify?
The amplified signal is inverted, so they invert it back
@@maryannetoldme6341 thanks
Could analog op amplifier work better. Also if we change the magnetic flux in the surrounding area would it affect all of our electronic system?
Thanks a lot. Just one mistake I think. 6:20 the inverting and non-inverting inputs have been connected, making it a single node. Voltage difference is always zero.
can you give more specifics on creating a voltage divider using resistors (mentioned @1:30)? just following the schematic at that part at the video "creates a voltage divider"? Man. why did i just buy and build two power dual output power supply kits from jameco (besides the fact that they'll come in handy at some point and jameco is awesome)
Omg I’ve just found this channel and I’ve never properly understood these dam things! Thank you!
Excellent review covers a lot of use cases, I'd have liked some of the images on screen longer.
But great information for revising theory.
Wonderful video highlighting the power of TH-cam
Great video! I own a Boulder 500AE NOS amp and this was a terrific tutorial. It is an op amp.
The best thing about OpAmps is they neither affect the previous circuit (high impedance) or the next circuit (low impedance). And you can control the output impedance by putting a series resistor, do whenever the output load is 0 ohms your impedance in the output will always be what you defined in the series resistor.
did not know that , nice to hear that , that piece of info is worth of gold
Thanks Kare, it is a nice lesson. So much to still discuss on opamps. I like them very much, IMHO they facilitate the design and implementation in a lot of projects.
U have shown differential circuit as Positive feedback??
I learned "virtual ground" is a big aspect to op-amps. I never fully grasped the concept to my satisfaction, but the way I understand it is the current between the two inputs is so small a virtual ground potential is present between them. That is if one of the inputs, either the inverting or non-inverting, is pinned to ground. Can anyone offer more on this?
It's a great video, and I would have loved to have it as a learning resource back in the day.
You understood it wrong. There is no such thing as a 'virtual ground potential'. In an inverting configuration, the non-inverting input is grounded and the inverting input presents a virtual ground because the opamp works to keep the voltages at both inputs the same. In this mode the opamp is sensing input current rather than voltage, as the voltage is always zero. That's why it is a virtual ground.