#281 

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!

Best preparation, best explanation, best voice and best demonstation avalable on the internet. 👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍 👏👏👏👏👏👏👏👏👏👏👏👏👏👏

Hi Alan, Very informative video with excellent visuals. Deserves more than just a thumbs up. 73 WB3BJU

A very nice video as usual, thank you! P.S. I really love the 'good, bad and ugly' thing.

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!

You are very good at this. Thank you for wanting to do this for us all

Wow! Thank you very much for this tutorial. Please keep them coming.

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.

All of your videos are very interesting. Thank you.

Very interesting and informative video. Thank you very much and keep up the excellent work ✌🏼

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.

I'm curious how the architecture is different in the transistor to change the parameters so drastically. Excellent stuff!

this was very insightful. thank you very much!

Thanks a lot. One more detailed look inside an interesting electronics chapter.

I really appreciated this video. Thanks!

Thanks for another good lesson.

Very useful. Thanks !

Oky have learned the concept. Liked...

Missing examples with the other values of base resistor and collector, when it doesn't get a deep saturation. Anyway great vid.

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?

Hello Alan, thanks for these precise explanations abour switching time. Great video. What kind of wire do you use for your homemade probe connector?

The Switching Loss means lower output voltage and lower amplitude? I'm confused on what the loss the loss of what?

Nice one , thank you.

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?

great!

I thought youtube have to ban such a porn!!!! Thumb up!

Let's see SCR's and TRIACs

How about FETs, can you please make a video about their switching parameters and to compare VS BJTs ?

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 RU-vid 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.

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

This devil in the details kind of video really gives you valuable insight into what's going on. Thanks.

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!!!

Fantastic video! Both enjoyable and informative.

Thanks for this great video!

Thanks for the excellent video as usual! I'm going to have to put together one of these test jigs - especially using your method of connecting probe leads to the pcb. Nice trick!

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!

Really good explanation!

Hi Alan, Excellent explanation. How does the hFE of a transistor affect its rise and fall times? Thanks a lot.

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.

Well done!

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)

great video. I wish you would also show, what does antiparallel diode + resistor to gate resistor do to waveforms

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!!!!!!!!!!!!!

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?

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!

Excellent

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.

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?

Thank you very much!!!!!

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.!

Great Video, you really helped me alot

I really like your videos !

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

Awesome video Alan, can you do this for FET's?

Great video.

What a nice surprise, I love this style of videos. Thank you! :o)

you are the best teacher ever! 73 PD1FR

This material would take someone many days to understand reading from a textbook.

Man, I just realized how much I missed your back to basics videos! Hope all is well, Alan

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!

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.

Excellent but... it is a bit annoying when we are looking at your paper text and diagrams and it keeps moving around. I would suggest putting the paper on the desk and not touching it while talking. We all shake or move papers while doing this but on video (Hfe of our screens to the real paper size!) it can be a bit distracting. *That being said, as always I really enjoyed this video. Thumbs up.*

You explain things so easy to understand! I wish I had these videos when I was in college.. (25 year ago LOL)

Extremely very good video! Thank you very much and it give deep help! Thx!

Well the BJT performance in switching is generally very depressing, you almost have to be desperate to use them (see IGBTs) :-P

I stumbled upon the phenomenon of storage time last night while testing a mosfet driver circuit. Interesting stuff!

Good video, Thanks... more videos like That, please...

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.

We work these same dynamics with the Klystron on Radar Systems...amazing devices.

Yes digital circuits went from TTL logic families, PMOS, NMOS, CMOS. Digital circuits had switching loss issues that is why they settled with CMOS for faster switching times and lower power consumption.

It's Awesome Alan! I am refreshing all my undergraduate concepts from your video before going to my master's :P

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.

Thanks for sharing. Very interesting topic.

EXCELLENT. NUFF said.

Thank you for all the detail!!!

I was hoping you would show without negative base voltage, just going back to 0v.

long live The Frisca

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?

Very interesting thanks

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%.

Awesome !...cheers.

Nice little fixture.

Awesome video, dude.

Great work!

Great video, would have liked to see some big TO3 power transistors in the mix.

Thank you

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!

Like 1K5 Dislike 4 that set a new RU-vid record almost 400:1. The dislike perhaps was happen accidentally.

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."

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?

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!

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.

How fast would the fall off be if you didn't drive the switch off negative?

you should show how long the storage time is with 0V turn-off drive

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!

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?

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.

Thanks 4 the refreshing ! 73 N8AUM

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.

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.