All You Need To Know About Op Amps To Fix Stuff. Part One - How Op-Amps Work
ฝัง
- เผยแพร่เมื่อ 8 ก.ค. 2024
- This video is sponsored by PCBWay For All Your PCB needs: free $5 discount coupon
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Let's take a look at Op Amps. These devices are used in a wide range of electronics and you need to have some understanding of how they work to be able to diagnose faults in these circuits. Part one covers the essential theory, using almost no maths. Part two will cover the practical side.
00:00:00 Intro
00:02:33 Op Amp Test PCB
00:07:44 What Is An Op Amp
00:13:52 Comparator
00:19:16 Buffer
00:25:44 Non Inverting Amplifier
00:30:38 Inverting Amplifier
00:35:36 Op Amps and Capacitors
00:40:41 What Op Amps Look Like
00:43:13 Other Considerations
00:48:32 Outro
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Thank you
Richard
Glad you enjoyed my board, and thanks for introducing it to others.
Hi there! Yes I really liked your boards and I do hope you appreciated the shout out. Credit where it is due.
To all watching - this is the guy who designed this excellent teaching aid - please hit subscribe if you liked it www.youtube.com/@IMSAIGuy
I'll be using your boards a lot more in part 2 next week, which will be the practical tutorial video. If you would like to have fun doing some sort of collab sometime let's get together 🙂
I have watched atleast 30 videos on Om Amps and they never really made sense.
YOU HAVE TAUGHT THIS SO WELL. With practical and mathematical examples and for a technician to understand!
THANK YOU THANK YOU THANK YOU!!!
Two of my favourit channels in one video. What a pleasure!
This was really interesting. I tried getting into electronics as a teenager, more decades ago than I care to count, and I encountered 741s quite often. I never really understood them, and particularly never grasped why they would require dual power rails. I'm trying to build up some knowledge again, this time properly, having the benefit of easier access to components and test equipment. I'll need to watch this video a couple more times to properly cement the knowledge in my brain, but it's time well spent if I finally manage to understand these devices after so many decades.
I finally understand how to use an op-amp - something that has previously remained a mystery. A brilliant video. Really looking forward to part 2.
That was a great refresher. Last studied 35 years ago 😳 so much needed!
Thank you Richard. As a beginner I seen lots of explanations regarding op amps. Yours wher the most useful to me personaly.Thank you.
Thanks Richard! You explain these things the way I have not seen elsewhere. 👍🏻
Simply the best video about OpAmps I've seen on TH-cam. Thank you!
Imsai guy has a great channel too.
Love these videos buddy.
Yeah he has a great channel !
After a bottle of brandy this video has left me wanting a hotdog!
Can't wait for part 2. I love your videos. Very informative and enlightening. I've learned quite a bit from watching them and I appreciate you sharing your knowledge. Keep up the great work!
@2:34 "These ones"? What?
Great information. Thank you.
Brilliant. Best explanation I’ve heard. Cheers.
Very good explanation. Other opamp configuations you see often:
opamp as a differential amplifier,
opamp a Schmitt trigger,
opamp as a precision rectifier,
opamp with feedback from the output of an additional external transistor amplifier.
That was really neat. Can't wait for part 2.
Hi Dicky, as you know I’m in Australia, it’s now 8:20pm here, and 9:20am in the Gran Canaria, just trying to work out if the live stream is happening, you 5pm today or tomorrow.. I hate time zones lol. Let me know mate please.. 🤙🏼🇦🇺
Joe from Australia 🤙🏼🇦🇺
Thank you Richard... been waiting for this ...
Great tutorial ! and Hi to the Imsai Guy if he's watching. You neatly covered the big trap for young players and that is 0V at the input ! many a perfect chip has been thrown in the bin with that one !...cheers.
Great tutorial - looking forward to Pt 2
Brilliant video. thank you so much. very informative.
Great video. Keep it up.
Richard, a very nice video covering basic principles and application of op amps. 👍😁
😊Great video
👍👍👍 damn you're such a good teacher !!
People repairing stuff would really be interested to know how to test op amps. You need to cover all the main types, LM741, LM358, NE4558, LM324, TL071, TL072, TL074, TL081, TL082, TL084 and possibly some others etc. It should be noted that opamps specifically made for voltage application often don't work correctly with audio applications (and vise-versa) even where the pinout and function is identical. For example in the past I was repairing an audio circuit that used a JRC3414. It has a pinout that matches LM358 but using that caused some strange faults with the audio (scratchy noise in the audio) so I had to source some less common JRC3414 chips. Also note on Ali there is a much more useful opamp test board. You should get one of those.
Yeah of course I will cover testing Op Amps in the next part
You can take a look at this video too th-cam.com/video/cGRPBV-_ZQc/w-d-xo.html
Love your channel, Richard. 😊
I was wondering, could you possibly do a video or series of videos on how to produce the Gerber files from a self designed project to use PCB Way's services?
I'm reasonably familiar with Tiny CAD free that I use for producing schematics, but don't know how to produce the PCB design and Gerber files to order PCBs from PCB Way.
What schematic / PCB CAD software do you recommend?
I feel like Im taking college level electronics....I want to build a car audio amplifier with some of these new Mosfets available...is there a high power Mosfet available with both PNP and NPN built in? or should I look to build it separately using individual MosFets? I was looking at the Infineon high voltage Mosfets but Im not sure how to pair them up or if I need to...
I'm new at this....I was thinking like a 10 channel amp with one pair of mosfets per channel...I see some 900v ones, just for example so I figure we should be able to drive a lot of channels with fewer Mosfets is my logic...let me know if anyone thinks thats out of line lol
Interesting devices! I'm interested in how they fail; do they usually go open or do they short?
In your buffer example I was thinking these may be ideal to control motor drivers from a micro controller to prevent it from being fried when motors or their drivers fail but that all would depend on if these fail by going open when they burn up.
Semiconductor devices that fail catestrophically (i.e. not just due to parametric shift) almost invariably initially fail short-circuit. If there is sufficient energy available from the external circuit then the device may open like a fuse, sometimes very violently.
An op amp to buffer an analog signal being fed to or from a microcontroller could help protect the controller in the event of failure in the power circuit. If you are dealing with digital signals, either as inputs or outputs, a simple digital buffer (e.g. 74xx04 for an inverting type) gives some extra measure of protection. Resistors can be a very big help. For example, if you use a digital gate to buffer a signal to/from the power circuitry, a resistor of 10k or even more between the processor and gate adds a lot of safety margin in terms of device protection. Most I/O pins have protective dodes that "clamp" the voltage to the supply rails, but you need to keep the current low, typically 5 mA or less, for the diodes to survive and do their job. You do have to keep in mind that reistance can cause delay in conjunction with input capacitance and may not play well with passive pull-up or pull-down schemes.
Optocouplers are even better as protective barriers, but of course they take quite a bit of board space, need drive currents of at least a milliamp or two,and tend to be "slow." Opto coupling an analog signal beyond any performance that is quite crude is rather complex and expensive.
You should be able fo find lots of application notes on protecting inputs and outputs.
@@d614gakadoug9 Many motor drivers have optocouplers built in these days.
That’s awesome!! IMSAIGuy was one of the first channels I subscribed to. He has an awesome channel.
I don't know how common it is but I was just fixing an SMPS with comparators instead of the TL431 programmable zener diode. You could mention this usage in the next video if it's common enough.
What specifically was the "comparator?"
It isn't impossible but very unlikely that a switcher would use comparators in the control loop other than in the pulse width modulator itself. It _is_ very common to use an op-amp that is open-loop at DC as an error amplifier but it operates in linear mode, not as a comparator.
A comparator _might_ be used for hysteritic ("bang-bang") control. This is sometimes done in low power circuits.
Where a TL431 is used for feedback in a switcher it is almost always used as the error amplifier, not just as a reference.
@@d614gakadoug9 The PWM IC was TEA1716T and the PSU was 22V 100W. There were no TL431 or zener diodes. There only was an AP4310 dual op amp and voltage reference IC with a resistive voltage divider on one input compared to output voltage. The other op-amp input wasn't easy to figure out. Both of the outputs were driving an optocoupler leading to the PWM IC (although through a transistor and other stuff). I actually changed the values of the voltage divider to get different output voltage and succeeded, although with glitches in output voltage. Why shouldn't a comparator/op-amp work instead of the TL431/zener?
If I replace an op amp , I always socket it . Any reason not too ?
PS cutting up sockets to make plug in connectors is absolutely genius 👍
In some circuitry a socket will make no practical difference. In high precision circuity as might be found in industrial electronics a socket can make a mess of performance.
If the op amp in question has a unity-gain bandwidth no more than a few megahertz, input offset voltage of some moderate fraction of a millivolt or more and input bias current some moderate fraction of a nanoampere or more a socket is likely to be OK. A socket introduces additional capacitance that can cause problems at very high frequency. It can increase leakage currents that can cause DC errors with very high precision amps or in circuits with very high impedances. They can (depending on plating material of pins of the IC and socket contacts) introduce another thermocouple junction at each pin that can cause DC error that may be important in circuits of very high precision. They can also degrade reliability in gear that must operate over a very wide temperature range or that is subjected to a lot of thermal cycling.
Failure to _properly_ clean the circuit board after replacing an amp can also cause serious problems in high precision and high impedance circuits. Proper cleaning can be quite difficult. A little isopropanol slopped around and crudely wiped off just won't cut it. If the board originally had a conformal coating it can be a colossal pain!
I have heard with non inverting buffers, if there is a resistor in the non inverting input, say R1 of a voltage divider, you should put an equal value resistor in the feedback path. Something to do balancing input bias currents. Those input currents that don't exist with the ideal op amp. Is that really necessary for accurate buffer ?
[edit] I neglected the mention of "buffer." Because the term "buffer" is almost always used for a unity gain (x1) configuration, it is the least sensitive to input offset errors. When higher gain is taken the input offset errors are multiplied by the gain so this issue can be much more of a problem in high gain applications. [end of edit]
With ordinary bipolar transistor op-amps balancing the resistances seen by the inputs does help to reduce the error due to input bias current. In your example with a voltage divider on the NII, you would use a feedback resistor approximately equal to the parallel combination of the resistors in the divider.
Whether you really need to do this depends on the specific op amp and the demands of the circuit. Unless the resistance at the input is quite high, the input bias current is high and there is need for the best precision possible with the amp you have chosen, you probably don't need to do it. It is easy to calculate the error you'll get if you don't do it.
With FET-input op amps it is very rarely of benefit because of the very low input bias current of such amps. Against that, you may be using a FET amp because of very high source impedance. Some precision amps with a bipolar input stage have internal bias current compensation circuitry and using external resistors in this fashion actually can make matters worse.
Resistors also contribute noise, which is often a consideration. You have to decide if the extra noise contributed by the resistor is more tolerable than the DC error you'd have without the resistor.
You'll find these things discussed in ap notes for op amps. Some of those from Analog Devices from many years ago are quite good.
Wow. Thanks for the detailed reply. Very helpful.
@@barryjensen296notes on opa2134 fet input show high distortion if input resistance is not similar.