Sir, I am an electrical engineering undergrad and i give you standing ovation on your every video. You've helped me understand many concepts and i consider you one of my lecturers. Keep up the good work!!!
You would be hard pressed to find a college lecturer that is able to give the hands on experience coupled with the highly technical theory side and the maths as well as Alan can. I can totally see your parallel as him as a pseudo lecturer.
no offense , but why are you telling everybody who knows something a Sir? That corporate culture long dead by now in everywhere in the world. Every exists in military and polices. Just address him with his name, he got a name. Just enough respect to the person who learn from and his time and courage is enough. If he have a Dr rate then address him with Dr. but not Sir, Sir is too formal.
@@dhammikaperera4059 Hi Dhammika. Not everyone (or every culture) is comfortable addressing someone by their first name, especially if they haven't met them in person. I agree with you that it seems too formal in some cases, but I consider it a title of respect.
I just love your videos! Not sure if you have a video on the subject but a video on the power dissipation during switching (MOSFETs, BJT's) would be fantastic. Thanks again for your videos!
Another great tutorial Alan. Thank you very much for taking the time to put these types of videos together to help folks that really want to learn the art of electronics. Your presentation is always clear, professional, and easy to follow. As a content creator myself I know this takes a lot of your time to put these together. You really have to do it for the love of the hobby because the pay from TH-cam is very little. What really gets me is someone comes by and gives a thumb down. This always makes me wonder why? Not like folks are paying for the free information. Alan I appreciate what you share.
I fully agree with all of the positive comments. You are certainly a 5 star and/or Gold content provider on YT. Thanks for all your time and dedication!!!!!!!!!!!!!
Hi, Alan! I have finally received my first ever HAM license on Sunday and wanted to give you a big thanks, since I consider you to be one of the people who inspired me to take up the hobby! Going down memory lane a little, I had first found your channel because I wanted to find a video on scope triggering just before I bought my first scope. A Tektronix 2235, by the way(Yep, I'm one of the family, too, lol). That was in November last year. And then I watched those seminars on scope applications with antique radios that you had hosted and it all went down from there haha! Anyways, I wish you many healthy, productive and fun years ahead! 73s!
I come here and watch your videos periodically and am really amazed at your vast knowledge and really superb delivery. But mostly I want to say thank you for taking the time to do this at all. You really help a lot of people all over the world understand things much better. Thank you. Mike K8MB.
With all the trolling on YT and FB it's a great comfort to know that guys like you exist and provide straight up great information with no BS. The internet is often a sewer, but there are oasis of intelligence here and there that make it worth it. Thank you!
First, I am VERY glad that you got the rise and fall times correct; I am disappointed by how many engineers get those backwards. Second, I love your probe test points and I wonder where you get those coil springs? Third, you can reduce the "storage" time by using the 74LSxx trick of placing Schottkey diodes between the base and collector. Fourth, the fall time MEASUREMENT depends substantially upon the collector resistance/collector capacitance RC time constant -- 220 x 10p = 2.2 ns -- the minimum fall time you can measure might be 2.2 ns if the Coss is 10 pF or larger. Whatever the Coss, the intrinsic fall time will be RC shorter than the measurement.
You've giving me a better understanding what's really involved with "switchers". They were somewhat mysterious to me with my "analog" mind. Thanks for taking the time to share!
Excellent presentation Alan :) !!! Showing the influence of both, the input signal and the operating conditions, which each manufacturer uses to their advantage, to improve the results in the tests of their devices.
Your capacity in delivering such well-structured and detailed tutorials, covering both the theoretical and experimental aspects is truly amazing. We are really grateful. Would you consider making a video on demonstrating and measuring the characteristic impedance of a transmission line and/or coax cable and its dependence on frequency?
I have several videos on transmission lines: th-cam.com/video/g_jxh0Qe_FY/w-d-xo.html th-cam.com/video/Il_eju4D_TM/w-d-xo.html th-cam.com/video/M1PgCOTDjvI/w-d-xo.html th-cam.com/video/TpIIftvQPFM/w-d-xo.html
Hi w2aeq. Great video. Do a follow up video where you add a speed up cap across the base resistor and show how it actually speeds up the switching speed. Then do a bakers clamp circuit which keep the transistor from going into deep saturation and thus mitigate storage delays. Great video. I will probably do a similar video on this subject on my channel. Robert
Wonderful video, Alan; I learned a lot. Many thanks. It would be great to see a follow-up showing a similar discussion and testing with MOSFETs. The varying gate charge characteristics -- especially in large power FETs -- would make for some interesting measurements. That, in turn, could lead to a video about how to properly drive a FET. Again, thanks. Your videos are the best of their kind!
Very good, I would expect to get this education at a higher level of college. My thoughts on this are that many transistor circuits used as a switch to take the load off of a microcontroller, or in some other similar circuit, won't matter much. But when the circuit involves much more complicated switching times that correlate with switching times elsewhere in the same circuit, that is where the selection, and tweaking of control parameters of each stage are important. The testing you are doing can be turned into a book of practical transistor data. You can simplify what each testing parameter means, and list the transistors in or of best to worst for that particular test. I would buy a book like that. In most cases, simple transistor circuits can work around any common transistor, but even those have their limits. Usually those limits are in power handling, and how fast or slow they are isn't of much concern, as long as they go off, and on with no noticeable delay. Other circuits involving audio, have requirements about low noise, and that is another area that can be tested. Thanks for the excellent way you explain things in great detail.
This also means that with sawtoothish drive waveforms you can shorten the storage time while still having a square wave at the collector. This may come in handy at some times where you want to minimize pulses to spread out
Thanks for the clip. Very interesting subject. BJTs are not really fast switches, FETs and even faster super conductor devices are better at it. However, there are circuits to improve the switching speed of BJTs, like totem pole for MOSFETs. In my opinion, it would have been good it you monitored emitter current to demonstrate that during transition net current entering BJT is not zero! (That is Ie != Ib + Ic during the transition)
Thank you very much for this visual. You did this BJT set up with a basic common Emitter circuit, I would really be interested in seeing it also done in a Common Base, and also a true Common Collector (reverse mode) set up if you can have the chance. Thanks again, and keep up the excellent work!
Hi Alan, thanks for such informative video. I have a question, when you were testing the RF diode and measuring the rise and fall time, I think you have to zoom in more horizontally as the scope relies on the horizontal resolution to give you an accurate rise and fall time. it would interesting to see what they would be on 400ns or 200ns per box scale if you still got the setup up and running.
That is a very good observation, and worthy of a little bit of discussion. Many (most?) digital scopes make their automated measurements on the waveform points shown in the display. Since most scopes have 1000 points (or less) resolution across the display, measurements like rise and fall time on very fast edges can be inaccurate if the horizontal scale is too slow and the edges are nearly vertical. It turns out that Tektronix scopes operate a little differently - they make their measurements on the full waveform record - not just the displayed points. You'll noticed from the annotations in the bottom of the scope screen that I have the scope set to use a 10,000 point waveform record, and the scope's sample rate is running at 1.25GS/s, based on this combination of record length and horizontal setting. That means that there is a 800ps interval between each time point. Therefore, there are probably 18 or 19 sample points on the 15ns edge, so the accuracy is still good. In fact, the scope will give me a "low resolution" warning if the sample rate isn't sufficient for a given measurement. As I said, a very good point that you raise, and something to really watch out for on many other digital scopes.
The hfe of the transistor change the storage time and a littlebit the switch off time. The storage time gets longer for high hfe transistors due to effect that the electrons in the charged base have to flow primary back to the base drive circuit. The discharging path from the base to the emitter is therefore less effective for a high hfe transistor. Cheers from Berlin
@@christophschuermann7920 On the other hand, a high β transistor may be able to be driven into saturation with a smaller base current. Sometimes the manufacturers specify Vce(sat) for high-gain transistors with Ib = Ic/20 instead of Ic/10. In that case, there will be less stored charge to remove, so it's somewhat "swings-and-roundabouts".
Thanks Alan! Another area of misty understanding gets blown away by the clear breeze of reason :-) I'll definitely be building one of these. Are the switching times pretty consistent among batches of transistors of the same type? Sorry, one more question; is the switching time, particularly thinking of the on time, what gives rise to the propagation delay in TTL ICs?
Switching times should be consistent from the same manufacturer for the same device type - there may be more variation when looking at other manufacturers of the same device. I would imagine that the TTL propagation delay is dominated by the storage time of saturated transistors, but I haven' studied this to state it definitively.
Great video. I've been wanting to do the same comparison between genuine 2N2222A transistors I've had for years in my parts bin, and the 100 I bought from AliExpress for real cheap (< $2), to see if there are any rise and fall time differences between them. Unfortunately, I haven't had the time to do that yet, and I was wondering if you've conducted such a test? Do you plan on doing any such tests in the future? Or a way to tell the difference between genuine parts and the Chinese knock-offs. Maybe a test fixture like what you have?
A homemade fixture like mine could certainly be used to understand the switching behavior differences, if any. But, other tests might be necessary depending on the application (amplifier, etc.). I haven't purchased any cheap knock-off parts, so have never done any comparisons.
Nice video Alan. Have you considered a follow-up video showing how to speed up the switching by using various techniques such as Baker clamps, parallel cap across base resistor and proportional base drive? RBSOA explanation would also be nice to see. Its almost a lost art nowadays with high speed MOSFETS.
It would have been interesting to see the switching speed vs temperature, like get a hot air gun or better yet an adjustable soldering iron so you can look at the relationship between temps and operating speeds.
Good and informative video. Thanks. I've been aware of MOSFET's gate capacitive issues, but your video has taught me bipolars aren't perfect either. The test was interesting, but would most applications use negative voltages to pull a transistor low to deplete it in switching application? When you mentioned that there was little of a test setup, I immediately thought of level shifting from 3.4v to 5v, or vice versa. Driving an 30ma LED from either a Raspberry PI's 3.3 paltry "general purpose I/O" pins or driving one or more LED's from an Arduino 5v pin would be an interesting response time test. I am not even sure if a PI can even power most opto-isolator/couplers, safely. An Arduino can handle an LED from a pin, but not more than one. For current draw LED's 20-30ma seems like a nice current draw for a test, though biasing aside most Arduino people just use a 1K resistor for current limiting because they close enough, most people have them, and when you are holding a hammer, everything looks like a nail. : ) Thanks again!
True - most applications wouldn't pull the base negative to turn off (unless it's specifically designed to minimize storage time), but that's the way that the test conditions are defined by the manufacturers.
Hi Alan, sorry to be a pain, but I wondered if you (or your subscribers) know of, or have a way of finding out, what a recommended replacement would be for RT1010 (NTC thermistor, 7.5 Ohm, 10% - I think 7A) on the A2 regulator board of the 24XXB 'scopes? There are two, the smaller, inboard one is not a problem, as the SG200 (5 Ohm, 5A) is still produced. There is one p/n for it in the 1989 Service Manual for the 2465B/2467B (75DJ7RK5-RO-220), and a Tek p/n in the 1993 edition (307-0350-00). The closest I've found so far is a 7 Ohm (within 10%) 10A part, but it is quite a bit larger and radial rather than axial. There is a gap at the junction of the leads and encapsulation of the old one, and the cold resistance has shifted upwards (I'm guessing moisture ingress thru the gap has caused this) to just under 10 Ohms. I could dry it out and re-seal the leads with very low viscosity epoxy, or use the over-sized part I found, but I'd really like to get a new part, closer to spec as it's in there for current inrush limiting on start-up. I totally understand if you are too busy, but maybe one of your viewers has the answer. I think I may have an addiction problem developing, though. I've got a 2465B n its way, an Ex-Sony Gmbh. owned one with a Tek cal sticker on it from '09. Happy days!
Very cool thing to experiment with and again a really nice, well explained video. One question though - do the parameters vary much between transistors of the same type? So will two different 2N2222 transistor exhibit about the same times?
They *shouldn't* vary much among the same device type from the same manufacturers - but beware of different manufacturers' devices - there may be some additional variations.
The differences in the generic house types is quite revealing. Some makers probably don't do much extensive testing if at all. Guess you get what you pay for especially when it comes to speed and quality.
Very interesting. While not related to bipolar transistors I would have found it interesting to see how a small fet would compare just to give a visual comparison of the switching times. Datasheets tell me the fet would be maybe 5x to 10x faster but I guess it really depends on the fet.
Great video as always! Thank you very much. Also it would be interesting to see Ts & Tf times without negative bias, just 0V at the base. I think Ts will incease by ≈50% or so. Still I'd think it's kinda missing in the video. But again, it's great anyway.!
It would be interesting to use these measurements to derive the SPICE models parameters for the part. If done correctly, the simulation should match the measurements over a wide range of conditions. Too bad the manufacturer's don't do this (correctly) for us. The procedure is in "Modeling the Bipolar Transistor" by Ian Getreu, and in the ICCAP software from Keysight EEsof.
The higher the switching time , the higher the switching loss , the smoother the signal? The Switching loss means that the transistors or FET's output amplitude voltage and current is lower when the switching time is higher in frequency?
A switching transistor dissipates the most power during the switching time. So, faster switching times are desired to minimize loss and device heating due to power dissipation.
Hi Alan, someone asked me what exactly does "PAD" stand for? Passive Attenuation Device? Or something else? I looked in the ARRL handbook and interestingly there isn't a definition in there. Thanks as alway, Vince.
Fantastic. Thank you. If you change the "rest time" between AWG pulses, does anything change within the "operating frequency" of the DUT? I haven't seen much information about switching performance near the speed limit. How do BPJs fail as they approach their speed limit?
Question: When the drive voltage went from negative to zero volts, right at the end of the sequence, you can see a llittle gulp of current on the base. My best informed guess is that that is the capacitance of the base being charged up from -ve to zero. Is that correct?
Sorry Alan, I'm not entirely clear on the sig-gen connections described at 11:24. The delayed add of the second channel is then more negative (-4 to -5v) than the 1st channel's positive (3v)? I'm thinking the popular "FeelTech FY6600" would need some independently isolated channels to do something so nice. I'll get over it I'm sure - but we get what we pay for.. :-(
The Pulse function of the generator allows me to set a LOW and HIGH value on the pulse waveform. But, I really want three votlages. I want to start at 0, have a positive pulse immediately followed by a negative pulse then return to 0. This is done by summing a positive pulse with an appropriately delayed negative pulse (both of which have 0V as their starting end ending points). By building it this way, I can independently adjust the VH and VL levels.
Nice explanation, thanks. How relatable is a test like this to op amps and slew rate? I built a simple go/no-go/linear output op amp tester a few weeks ago (no YT content created). That little project got me thinking about ways to test more op amp features directly. I built my tester with the ability to reconfigure the inverting/noninverting connections. I'm just a beginner hobbyist with what I would call a basic sub-fundamental understanding of op amps. My interest in a more advanced tester is more about thoroughly learning about op amps more than the need for a real tester. From what I currently understand I'm looking into ways to test slew rate, input bias current, offset, quiescent current, and linearity. I will probably never get around to building something, but I hope to learn a bit. Any suggestions or ideas are much appreciated. I've been attempting to learn basic microcontrollers from the OSHW AVR transistor tester project. I'm really curious about what kind of op amp tester I could make using a simple AVR. Any suggestions or references to similar circuits/projects would be much appreciated. Regardless, thanks again for the upload Alan. -Jake
Alan, what do you call those sockets that your probes are plugging into? I can wind my own ground connectors like you have here but where do I get the tip connectors? Are they the same as the sockets you are using for the components? I have to start probing test circuits like this when able. Thanks.
Wow, Mill Max make a HUGE selection. Do you have the part number? I am looking now on Mouser, Newark and Digikey... I don't want to spend money on the wrong ones and some of those are quite expensive. What do you recommend? Thanks for you time!
I typically keep 2 or three sizes on hand. Yeah, they aren't cheapies. The ones used in this video are Mouser p/n: 575-032700. The other sizes I have on hand are 575-029200 and 575-066700.
Hi Alan, appears that the link to PDF is down. Getting error "Destination Unknown Everything's working on our side, so the short link you clicked is either wrong or has been retired."
Brilliant video and a great learning resource. I like to run your demonstrations myself as I learn even more but this one has got me stuck. My arbitrary waveform generator only produces 0 - 2V so have been trying to figure out a way of amplifying that so I can at least try 0 - 5V. The tricky bit is finding a circuit that will provide fast enough edges. Any suggestions?
The little 74AC14 based oscillator that I've shown in videos like this (th-cam.com/video/NuXitMK3HSA/w-d-xo.html) and this (th-cam.com/video/CQTGhcjE7Ww/w-d-xo.html) would work well.
Whilst waiting for 74AC14 to arrive I tried a 555 as the pulse source which allows me to drive the DUT with 0 to 7V. I'm getting sensible results now but one question if I may. The 555 pulses have rise and fall times around 44nS - does the speed of the driving pulse affect the measured rise and fall times of the transistor?
@@robinharris4706 It certainly can. If the pulse source is slower than the transistor, then all you'll be measuring is the speed of the pulse source, not the speed of the resistor. To get an accurate measurement of the transistor, the pulse source needs to be faster than the transistor switching speed.
@@w2aew Thanks - makes sense! I am measuring collector rise and fall times in the 20nS range even though the driving pulse is around 44nS. Should have a 74AC14 this week so will then compare results with that driving in place of the 555. The amount I have learnt about the humble transistor by doing these experiments is staggering! Watching the video is great but setting up and trying the circuits is awesome.
Both the storage time and the IC fall time will increase. For the couple of transistors shown, these parameters increase 50-100% without negative pulse of -1V.
Great video! That is useful in my work. I’m curious if this would vary over temperature. My intuition isn’t very good, but I would guess it would, mainly since almost everything a transistor does varies with temperature. You’ve given me some good ideas for some experiments. (I’ve only got a 2021, so I’m suffering from AFG envy though.) Thanks!
The loss is a loss of efficiency. Switching regulators are used when high efficiency is needed. Efficiency is the measure of power output divided by the power input. The desire is to have this as high as possible. Any power (heat) wasted in the power conversion circuitry is lost and not delivered to the load. Thus, the power dissipated by the device when it is switching on or off is wasted power, and is referred to as switching loss.
That was very interesting results!!! I have a ---- IRF 250 (200Volt @30amp Power Mosfet) that I have been playing with, and was wondering if you could run the same tests on it, as the video I just watched. I don't have near the type of test equipment that you have. I've been working on running a Kind of 3Phase motor I wound, And can run it up very fast with different input pulse rates, but won't run on any kind of load. Maybe they are not used for that kind of use.
Or having plenty of money. I would rarely need one, but it would be fun to have. I rarely even need my analog Tek 2465A DV oscilloscope to diagnose a problem with a device. But it's fun to play and learn with. My scope is still doing great after my battery change in it. Thanks again for your help.
Thanks yes i get it. But most circuits specifications don't list in the spec the switching loss value they only tell you the power efficiency. So the switching loss value is included in the power efficiency specification it seems its "not separated" in the specifications? What I'm confused about is that all transistors and FETS will have a resistances between the switching transition which is what the switching loss it from the heat dissipated but how would the transistors and FET components have very low switching loss when you will always have that transition resistance and heat dissipation while the transistor and FETS are switching on and off. Yes lower voltage and faster switching frequency helps with the switching loss and heat dissipation but still the transistors and FETS transistor resistance will always do a problem. I'm not sure how the EE designers will get away from this because it will always be there so I have no idea how to lower switching loss. What else can lower switching loss?
There are different sources of losses in switching regulator circuits - the manufacturers typically list only the total efficiency. It is the *designers* that will measure individual loss sources such as switching loss. Switching loss is worse with faster switching frequencies because you switch more often. The key to minimizing switching loss is to switch quickly, so that the transistor doesn't spend much time between the "fully on" and "fully off" states.
Best preparation, best explanation, best voice and best demonstation avalable on the internet. 👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍
👏👏👏👏👏👏👏👏👏👏👏👏👏👏
Sir, I am an electrical engineering undergrad and i give you standing ovation on your every video. You've helped me understand many concepts and i consider you one of my lecturers. Keep up the good work!!!
You would be hard pressed to find a college lecturer that is able to give the hands on experience coupled with the highly technical theory side and the maths as well as Alan can. I can totally see your parallel as him as a pseudo lecturer.
I agree. You can learn a lot from Paul at Mr. Carlson's Lab as well.
no offense , but why are you telling everybody who knows something a Sir? That corporate culture long dead by now in everywhere in the world. Every exists in military and polices. Just address him with his name, he got a name. Just enough respect to the person who learn from and his time and courage is enough. If he have a Dr rate then address him with Dr. but not Sir, Sir is too formal.
@@dhammikaperera4059 Hi Dhammika. Not everyone (or every culture) is comfortable addressing someone by their first name, especially if they haven't met them in person. I agree with you that it seems too formal in some cases, but I consider it a title of respect.
Really good explanation!
I just love your videos! Not sure if you have a video on the subject but a video on the power dissipation during switching (MOSFETs, BJT's) would be fantastic. Thanks again for your videos!
I did a video on that, but it is on the Tektronix youtube channel: th-cam.com/video/e3GjBcjP6e0/w-d-xo.html
Excellent
This devil in the details kind of video really gives you valuable insight into what's going on. Thanks.
Another great tutorial Alan. Thank you very much for taking the time to put these types of videos together to help folks that really want to learn the art of electronics. Your presentation is always clear, professional, and easy to follow. As a content creator myself I know this takes a lot of your time to put these together. You really have to do it for the love of the hobby because the pay from TH-cam is very little. What really gets me is someone comes by and gives a thumb down. This always makes me wonder why? Not like folks are paying for the free information. Alan I appreciate what you share.
I fully agree with all of the positive comments. You are certainly a 5 star and/or Gold content provider on YT. Thanks for all your time and dedication!!!!!!!!!!!!!
Hi, Alan!
I have finally received my first ever HAM license on Sunday and wanted to give you a big thanks, since I consider you to be one of the people who inspired me to take up the hobby!
Going down memory lane a little, I had first found your channel because I wanted to find a video on scope triggering just before I bought my first scope. A Tektronix 2235, by the way(Yep, I'm one of the family, too, lol). That was in November last year. And then I watched those seminars on scope applications with antique radios that you had hosted and it all went down from there haha!
Anyways, I wish you many healthy, productive and fun years ahead!
73s!
Congratulations on earning your ticket - that's great! Very nice to hear that I've helped you along the way.
I come here and watch your videos periodically and am really amazed at your vast knowledge and really superb delivery. But mostly I want to say thank you for taking the time to do this at all. You really help a lot of people all over the world understand things much better. Thank you. Mike K8MB.
Well done!
With all the trolling on YT and FB it's a great comfort to know that guys like you exist and provide straight up great information with no BS. The internet is often a sewer, but there are oasis of intelligence here and there that make it worth it. Thank you!
I really like your videos !
i tried measuring the rise time of a mps2222a recently and now i know one way of how they do it. thanks, this helps a ton.
Great Video, you really helped me alot
First, I am VERY glad that you got the rise and fall times correct; I am disappointed by how many engineers get those backwards. Second, I love your probe test points and I wonder where you get those coil springs? Third, you can reduce the "storage" time by using the 74LSxx trick of placing Schottkey diodes between the base and collector. Fourth, the fall time MEASUREMENT depends substantially upon the collector resistance/collector capacitance RC time constant -- 220 x 10p = 2.2 ns -- the minimum fall time you can measure might be 2.2 ns if the Coss is 10 pF or larger. Whatever the Coss, the intrinsic fall time will be RC shorter than the measurement.
Great video.
You've giving me a better understanding what's really involved with "switchers". They were somewhat mysterious to me with my "analog" mind. Thanks for taking the time to share!
I stumbled upon the phenomenon of storage time last night while testing a mosfet driver circuit. Interesting stuff!
Excellent presentation Alan :) !!! Showing the influence of both, the input signal and the operating conditions, which each manufacturer uses to their advantage, to improve the results in the tests of their devices.
Your capacity in delivering such well-structured and detailed tutorials, covering both the theoretical and experimental aspects is truly amazing. We are really grateful. Would you consider making a video on demonstrating and measuring the characteristic impedance of a transmission line and/or coax cable and its dependence on frequency?
I have several videos on transmission lines:
th-cam.com/video/g_jxh0Qe_FY/w-d-xo.html
th-cam.com/video/Il_eju4D_TM/w-d-xo.html
th-cam.com/video/M1PgCOTDjvI/w-d-xo.html
th-cam.com/video/TpIIftvQPFM/w-d-xo.html
w2aew thanks for the links!
Hi w2aeq. Great video. Do a follow up video where you add a speed up cap across the base resistor and show how it actually speeds up the switching speed. Then do a bakers clamp circuit which keep the transistor from going into deep saturation and thus mitigate storage delays. Great video. I will probably do a similar video on this subject on my channel. Robert
Agreed! I'd love to see a video clearly explaining how to get much faster switching with a BJT
Wonderful video, Alan; I learned a lot. Many thanks. It would be great to see a follow-up showing a similar discussion and testing with MOSFETs. The varying gate charge characteristics -- especially in large power FETs -- would make for some interesting measurements. That, in turn, could lead to a video about how to properly drive a FET.
Again, thanks. Your videos are the best of their kind!
you are the best teacher ever! 73 PD1FR
Fantastic video! Both enjoyable and informative.
Man, I just realized how much I missed your back to basics videos! Hope all is well, Alan
You are very good at this. Thank you for wanting to do this for us all
Very good, I would expect to get this education at a higher level of college. My thoughts on this are that many transistor circuits used as a switch to take the load off of a microcontroller, or in some other similar circuit, won't matter much. But when the circuit involves much more complicated switching times that correlate with switching times elsewhere in the same circuit, that is where the selection, and tweaking of control parameters of each stage are important. The testing you are doing can be turned into a book of practical transistor data. You can simplify what each testing parameter means, and list the transistors in or of best to worst for that particular test. I would buy a book like that. In most cases, simple transistor circuits can work around any common transistor, but even those have their limits. Usually those limits are in power handling, and how fast or slow they are isn't of much concern, as long as they go off, and on with no noticeable delay. Other circuits involving audio, have requirements about low noise, and that is another area that can be tested. Thanks for the excellent way you explain things in great detail.
Hi Alan,
Very informative video with excellent visuals. Deserves more than just a thumbs up. 73 WB3BJU
How about FETs, can you please make a video about their switching parameters and to compare VS BJTs ?
Me too
A very nice video as usual, thank you!
P.S. I really love the 'good, bad and ugly' thing.
It's Awesome Alan! I am refreshing all my undergraduate concepts from your video before going to my master's :P
great video. I wish you would also show, what does antiparallel diode + resistor to gate resistor do to waveforms
This also means that with sawtoothish drive waveforms you can shorten the storage time while still having a square wave at the collector. This may come in handy at some times where you want to minimize pulses to spread out
All of your videos are very interesting. Thank you.
Thanks for the clip. Very interesting subject. BJTs are not really fast switches, FETs and even faster super conductor devices are better at it.
However, there are circuits to improve the switching speed of BJTs, like totem pole for MOSFETs.
In my opinion, it would have been good it you monitored emitter current to demonstrate that during transition net current entering BJT is not zero! (That is Ie != Ib + Ic during the transition)
You explain things so easy to understand! I wish I had these videos when I was in college.. (25 year ago LOL)
Thank you very much for this visual. You did this BJT set up with a basic common Emitter circuit, I would really be interested in seeing it also done in a Common Base, and also a true Common Collector (reverse mode) set up if you can have the chance. Thanks again, and keep up the excellent work!
Hi Alan,
thanks for such informative video.
I have a question, when you were testing the RF diode and measuring the rise and fall time, I think you have to zoom in more horizontally as the scope relies on the horizontal resolution to give you an accurate rise and fall time. it would interesting to see what they would be on 400ns or 200ns per box scale if you still got the setup up and running.
That is a very good observation, and worthy of a little bit of discussion. Many (most?) digital scopes make their automated measurements on the waveform points shown in the display. Since most scopes have 1000 points (or less) resolution across the display, measurements like rise and fall time on very fast edges can be inaccurate if the horizontal scale is too slow and the edges are nearly vertical. It turns out that Tektronix scopes operate a little differently - they make their measurements on the full waveform record - not just the displayed points. You'll noticed from the annotations in the bottom of the scope screen that I have the scope set to use a 10,000 point waveform record, and the scope's sample rate is running at 1.25GS/s, based on this combination of record length and horizontal setting. That means that there is a 800ps interval between each time point. Therefore, there are probably 18 or 19 sample points on the 15ns edge, so the accuracy is still good. In fact, the scope will give me a "low resolution" warning if the sample rate isn't sufficient for a given measurement. As I said, a very good point that you raise, and something to really watch out for on many other digital scopes.
Very interesting and informative video. Thank you very much and keep up the excellent work ✌🏼
Hi Alan, Excellent explanation. How does the hFE of a transistor affect its rise and fall times? Thanks a lot.
I didn't measure that, but I suspect that the affect is minor.
The hfe of the transistor change the storage time and a littlebit the switch off time. The storage time gets longer for high hfe transistors due to effect that the electrons in the charged base have to flow primary back to the base drive circuit. The discharging path from the base to the emitter is therefore less effective for a high hfe transistor. Cheers from Berlin
@@christophschuermann7920 On the other hand, a high β transistor may be able to be driven into saturation with a smaller base current. Sometimes the manufacturers specify Vce(sat) for high-gain transistors with Ib = Ic/20 instead of Ic/10. In that case, there will be less stored charge to remove, so it's somewhat "swings-and-roundabouts".
Wow! Thank you very much for this tutorial. Please keep them coming.
Thanks Alan! Another area of misty understanding gets blown away by the clear breeze of reason :-) I'll definitely be building one of these. Are the switching times pretty consistent among batches of transistors of the same type?
Sorry, one more question; is the switching time, particularly thinking of the on time, what gives rise to the propagation delay in TTL ICs?
Switching times should be consistent from the same manufacturer for the same device type - there may be more variation when looking at other manufacturers of the same device. I would imagine that the TTL propagation delay is dominated by the storage time of saturated transistors, but I haven' studied this to state it definitively.
If I'm not mistaken, at 05:28 you said that the delay time is measured from 90% of the input waveform but you pointed at 10%.
Good catch - a little verbal mistake. (every one of my videos has a few, unfortunately).
Great video.
I've been wanting to do the same comparison between genuine 2N2222A transistors I've had for years in my parts bin, and the 100 I bought from AliExpress for real cheap (< $2), to see if there are any rise and fall time differences between them.
Unfortunately, I haven't had the time to do that yet, and I was wondering if you've conducted such a test?
Do you plan on doing any such tests in the future? Or a way to tell the difference between genuine parts and the Chinese knock-offs. Maybe a test fixture like what you have?
A homemade fixture like mine could certainly be used to understand the switching behavior differences, if any. But, other tests might be necessary depending on the application (amplifier, etc.). I haven't purchased any cheap knock-off parts, so have never done any comparisons.
Thanks. I had to ask before doing it myself. I will give it a go since I need to know if the Chinese stuff is worth buying or not.
Awesome video Alan, can you do this for FET's?
Thank you for all the detail!!!
Thanks for this great video!
I love your scope probe connection. I will do a similar thing on my next project. Love your videos and excellent presentations. 73
I did an entire video dedicated to making those high performance probe "sockets".
Thanks for another good lesson.
We work these same dynamics with the Klystron on Radar Systems...amazing devices.
Awesome video, dude.
Thanks a lot. One more detailed look inside an interesting electronics chapter.
Nice video Alan. Have you considered a follow-up video showing how to speed up the switching by using various techniques such as Baker clamps, parallel cap across base resistor and proportional base drive? RBSOA explanation would also be nice to see.
Its almost a lost art nowadays with high speed MOSFETS.
What a nice surprise, I love this style of videos.
Thank you!
:o)
It would have been interesting to see the switching speed vs temperature, like get a hot air gun or better yet an adjustable soldering iron so you can look at the relationship between temps and operating speeds.
Extremely very good video! Thank you very much and it give deep help! Thx!
this was very insightful. thank you very much!
Good and informative video. Thanks. I've been aware of MOSFET's gate capacitive issues, but your video has taught me bipolars aren't perfect either.
The test was interesting, but would most applications use negative voltages to pull a transistor low to deplete it in switching application?
When you mentioned that there was little of a test setup, I immediately thought of level shifting from 3.4v to 5v, or vice versa.
Driving an 30ma LED from either a Raspberry PI's 3.3 paltry "general purpose I/O" pins or driving one or more LED's from an Arduino 5v pin would be an interesting response time test. I am not even sure if a PI can even power most opto-isolator/couplers, safely.
An Arduino can handle an LED from a pin, but not more than one. For current draw LED's 20-30ma seems like a nice current draw for a test, though biasing aside most Arduino people just use a 1K resistor for current limiting because they close enough, most people have them, and when you are holding a hammer, everything looks like a nail. : )
Thanks again!
True - most applications wouldn't pull the base negative to turn off (unless it's specifically designed to minimize storage time), but that's the way that the test conditions are defined by the manufacturers.
Hi Alan, sorry to be a pain, but I wondered if you (or your subscribers) know of, or have a way of finding out, what a recommended replacement would be for RT1010 (NTC thermistor, 7.5 Ohm, 10% - I think 7A) on the A2 regulator board of the 24XXB 'scopes? There are two, the smaller, inboard one is not a problem, as the SG200 (5 Ohm, 5A) is still produced.
There is one p/n for it in the 1989 Service Manual for the 2465B/2467B (75DJ7RK5-RO-220), and a Tek p/n in the 1993 edition (307-0350-00). The closest I've found so far is a 7 Ohm (within 10%) 10A part, but it is quite a bit larger and radial rather than axial.
There is a gap at the junction of the leads and encapsulation of the old one, and the cold resistance has shifted upwards (I'm guessing moisture ingress thru the gap has caused this) to just under 10 Ohms. I could dry it out and re-seal the leads with very low viscosity epoxy, or use the over-sized part I found, but I'd really like to get a new part, closer to spec as it's in there for current inrush limiting on start-up.
I totally understand if you are too busy, but maybe one of your viewers has the answer.
I think I may have an addiction problem developing, though. I've got a 2465B n its way, an Ex-Sony Gmbh. owned one with a Tek cal sticker on it from '09. Happy days!
It couldn't hurt to send a note over to the nice guys at VintageTEK.org. They may know of a replacement, or even a source of an original.
Great idea, i shall give it a whirl! Thank you.
Nice little fixture.
I really appreciated this video. Thanks!
Very cool thing to experiment with and again a really nice, well explained video. One question though - do the parameters vary much between transistors of the same type? So will two different 2N2222 transistor exhibit about the same times?
They *shouldn't* vary much among the same device type from the same manufacturers - but beware of different manufacturers' devices - there may be some additional variations.
Thanks!
Great work!
The differences in the generic house types is quite revealing. Some makers probably don't do much extensive testing if at all. Guess you get what you pay for especially when it comes to speed and quality.
I'm curious how the architecture is different in the transistor to change the parameters so drastically. Excellent stuff!
Very interesting. While not related to bipolar transistors I would have found it interesting to see how a small fet would compare just to give a visual comparison of the switching times. Datasheets tell me the fet would be maybe 5x to 10x faster but I guess it really depends on the fet.
Great video, would have liked to see some big TO3 power transistors in the mix.
Great video as always! Thank you very much.
Also it would be interesting to see Ts & Tf times without negative bias, just 0V at the base. I think Ts will incease by ≈50% or so. Still I'd think it's kinda missing in the video.
But again, it's great anyway.!
Yeah, I should've done that.
Thank you very much!!!!!
It would be interesting to use these measurements to derive the SPICE models parameters for the part. If done correctly, the simulation should match the measurements over a wide range of conditions. Too bad the manufacturer's don't do this (correctly) for us. The procedure is in "Modeling the Bipolar Transistor" by Ian Getreu, and in the ICCAP software from Keysight EEsof.
Thanks for sharing. Very interesting topic.
Good video, Thanks... more videos like That, please...
Very useful. Thanks !
Would be interesting to see the behavior of large power transistors as well.
The higher the switching time , the higher the switching loss , the smoother the signal? The Switching loss means that the transistors or FET's output amplitude voltage and current is lower when the switching time is higher in frequency?
A switching transistor dissipates the most power during the switching time. So, faster switching times are desired to minimize loss and device heating due to power dissipation.
Hello Alan,
thanks for these precise explanations abour switching time. Great video. What kind of wire do you use for your homemade probe connector?
Hi Alan, someone asked me what exactly does "PAD" stand for? Passive Attenuation Device? Or something else? I looked in the ARRL handbook and interestingly there isn't a definition in there. Thanks as alway, Vince.
I always thought it was because they "pad down" a signal, but I really don't know the true answer.
No worries, Thank you.
Fantastic. Thank you. If you change the "rest time" between AWG pulses, does anything change within the "operating frequency" of the DUT? I haven't seen much information about switching performance near the speed limit. How do BPJs fail as they approach their speed limit?
Question: When the drive voltage went from negative to zero volts, right at the end of the sequence, you can see a llittle gulp of current on the base. My best informed guess is that that is the capacitance of the base being charged up from -ve to zero. Is that correct?
Yes, I believe that you are correct.
Sorry Alan, I'm not entirely clear on the sig-gen connections described at 11:24. The delayed add of the second channel is then more negative (-4 to -5v) than the 1st channel's positive (3v)? I'm thinking the popular "FeelTech FY6600" would need some independently isolated channels to do something so nice. I'll get over it I'm sure - but we get what we pay for.. :-(
The Pulse function of the generator allows me to set a LOW and HIGH value on the pulse waveform. But, I really want three votlages. I want to start at 0, have a positive pulse immediately followed by a negative pulse then return to 0. This is done by summing a positive pulse with an appropriately delayed negative pulse (both of which have 0V as their starting end ending points). By building it this way, I can independently adjust the VH and VL levels.
Sounds like a feature Tektronix should be putting into their next models or firmware updates. I'm sure it would be easy to implement.
Oky have learned the concept. Liked...
Excellent video.
Thank you very much!
Nice explanation, thanks.
How relatable is a test like this to op amps and slew rate?
I built a simple go/no-go/linear output op amp tester a few weeks ago (no YT content created). That little project got me thinking about ways to test more op amp features directly. I built my tester with the ability to reconfigure the inverting/noninverting connections. I'm just a beginner hobbyist with what I would call a basic sub-fundamental understanding of op amps. My interest in a more advanced tester is more about thoroughly learning about op amps more than the need for a real tester. From what I currently understand I'm looking into ways to test slew rate, input bias current, offset, quiescent current, and linearity. I will probably never get around to building something, but I hope to learn a bit. Any suggestions or ideas are much appreciated. I've been attempting to learn basic microcontrollers from the OSHW AVR transistor tester project. I'm really curious about what kind of op amp tester I could make using a simple AVR. Any suggestions or references to similar circuits/projects would be much appreciated.
Regardless, thanks again for the upload Alan.
-Jake
This would not be suitable for op amp slew rate. Check out my video on op amp gain-bandwidth product and slew rate...
Alan, what do you call those sockets that your probes are plugging into? I can wind my own ground connectors like you have here but where do I get the tip connectors? Are they the same as the sockets you are using for the components? I have to start probing test circuits like this when able. Thanks.
They are pin sockets, also called pin receptacles. These are made by Mill Max. The same ones I used for the components.
Wow, Mill Max make a HUGE selection. Do you have the part number? I am looking now on Mouser, Newark and Digikey... I don't want to spend money on the wrong ones and some of those are quite expensive. What do you recommend? Thanks for you time!
I typically keep 2 or three sizes on hand. Yeah, they aren't cheapies. The ones used in this video are Mouser p/n: 575-032700. The other sizes I have on hand are 575-029200 and 575-066700.
Hi Alan, appears that the link to PDF is down. Getting error "Destination
Unknown
Everything's working on our side, so the short link you clicked is either wrong or has been retired."
I've updated the link. Here is the link copied here as well:
www.qsl.net/w2aew/youtube/bipolar_transistor_switching_time.pdf
Brilliant video and a great learning resource. I like to run your demonstrations myself as I learn even more but this one has got me stuck. My arbitrary waveform generator only produces 0 - 2V so have been trying to figure out a way of amplifying that so I can at least try 0 - 5V. The tricky bit is finding a circuit that will provide fast enough edges. Any suggestions?
The little 74AC14 based oscillator that I've shown in videos like this (th-cam.com/video/NuXitMK3HSA/w-d-xo.html) and this (th-cam.com/video/CQTGhcjE7Ww/w-d-xo.html) would work well.
@@w2aew Great suggestion - will get on with building that oscillator. Simple and elegant. Thanks for taking time to reply once again.
Whilst waiting for 74AC14 to arrive I tried a 555 as the pulse source which allows me to drive the DUT with 0 to 7V. I'm getting sensible results now but one question if I may. The 555 pulses have rise and fall times around 44nS - does the speed of the driving pulse affect the measured rise and fall times of the transistor?
@@robinharris4706 It certainly can. If the pulse source is slower than the transistor, then all you'll be measuring is the speed of the pulse source, not the speed of the resistor. To get an accurate measurement of the transistor, the pulse source needs to be faster than the transistor switching speed.
@@w2aew Thanks - makes sense! I am measuring collector rise and fall times in the 20nS range even though the driving pulse is around 44nS. Should have a 74AC14 this week so will then compare results with that driving in place of the 555.
The amount I have learnt about the humble transistor by doing these experiments is staggering! Watching the video is great but setting up and trying the circuits is awesome.
Very interesting thanks
How fast would the fall off be if you didn't drive the switch off negative?
Both the storage time and the IC fall time will increase. For the couple of transistors shown, these parameters increase 50-100% without negative pulse of -1V.
Great video! That is useful in my work. I’m curious if this would vary over temperature. My intuition isn’t very good, but I would guess it would, mainly since almost everything a transistor does varies with temperature. You’ve given me some good ideas for some experiments. (I’ve only got a 2021, so I’m suffering from AFG envy though.) Thanks!
EXCELLENT. NUFF said.
Thank you very much!
I found the answer in the #111: How to make a high performance oscilloscope probe socket.
Thanks...
Thank you
The Switching Loss means lower output voltage and lower amplitude? I'm confused on what the loss the loss of what?
The loss is a loss of efficiency. Switching regulators are used when high efficiency is needed. Efficiency is the measure of power output divided by the power input. The desire is to have this as high as possible. Any power (heat) wasted in the power conversion circuitry is lost and not delivered to the load. Thus, the power dissipated by the device when it is switching on or off is wasted power, and is referred to as switching loss.
That was very interesting results!!!
I have a ---- IRF 250 (200Volt @30amp Power Mosfet) that I have been playing with, and was wondering if you could run the same tests on it, as the video I just watched. I don't have near the type of test equipment that you have. I've been working on running a Kind of 3Phase motor I wound, And can run it up very fast with different input pulse rates, but won't run on any kind of load. Maybe they are not used for that kind of use.
Pretty cool. Thanks Alan. I wish I could afford one of those MDO's.
It's one of the great benefits of working for Tek ;-)
Or having plenty of money. I would rarely need one, but it would be fun to have. I rarely even need my analog Tek 2465A DV oscilloscope to diagnose a problem with a device. But it's fun to play and learn with. My scope is still doing great after my battery change in it. Thanks again for your help.
Thanks yes i get it. But most circuits specifications don't list in the spec the switching loss value they only tell you the power efficiency. So the switching loss value is included in the power efficiency specification it seems its "not separated" in the specifications? What I'm confused about is that all transistors and FETS will have a resistances between the switching transition which is what the switching loss it from the heat dissipated but how would the transistors and FET components have very low switching loss when you will always have that transition resistance and heat dissipation while the transistor and FETS are switching on and off. Yes lower voltage and faster switching frequency helps with the switching loss and heat dissipation but still the transistors and FETS transistor resistance will always do a problem. I'm not sure how the EE designers will get away from this because it will always be there so I have no idea how to lower switching loss. What else can lower switching loss?
There are different sources of losses in switching regulator circuits - the manufacturers typically list only the total efficiency. It is the *designers* that will measure individual loss sources such as switching loss. Switching loss is worse with faster switching frequencies because you switch more often. The key to minimizing switching loss is to switch quickly, so that the transistor doesn't spend much time between the "fully on" and "fully off" states.
Nice one , thank you.
Awesome !...cheers.