In the world dominated by Java, ARM, ... your videos "back to the basics" are awesome! They are like shake off the dust from my analog soul. I love them and keep on going!
There is no analog, digital and pulse electronics. All is electromagnetic field theory. Analog and digital are just simplified theories. Nowadays microprocessor systems should be analyzed via analog and field theories because of their speed. Tracks on PCB are not digital connections but transmission lines with impedance (frequently differential pairs) and sometimes tracks are so long and bit rates so high that track works like a shift register and you can find several bits on one track one following another. So in fact we live now in analog word more than 20 or 40 years ago. Moreover EMC problems mixes digital with RF technology. Digital world is only for software boys, who do not understand what is happening inside the box :)
***** So true, there is some beauty in making something work with just a couple of transistors. I am fairly experienced in electronics but i keep using mostly opamps for any analog stuff. Thanks for teaching me new things
Codi Jack that's awesome comment. Number of engineers working on such discrete analog circuits, power amplifiers have reduced a lot. But Alan's videos always give us hope.
I have studied about this in amplifier design during my college days and seen in many transistor power amps… but after 29 years I am seeing working of this circuit in a scope. Awesome to see this ….. Thanks man… you rock.
I love how you go really deep into components analysis and let me discover some new feature every time. These are the best videos about electronics that can be found on youtube. And I always wish I was as smart as you are!
Brilliant! Thank you. I know this video goes back a bit, but it is sincerely appreciated, a super clear explanation. I am researching Vbe mulipliers as I want to come up with an alternative to the multi-diode bias spreaders used in vintage hifi. The breadboard will be coming out very soon!
Thank you. I have a clear headed understanding of it thanks so much. People like you change the lives of people like me. People like you empower and give confidence to people like me. Just thought you should know that.
excellent video, Alan! cristal clear explanation, the use of the oscilloscope clarify and complement a lot the theoretical discussion. I have to say I am impressed by the clealiness of your written material. It should be published as a book a it is! congrats!
I'm subscribed to many RU-vid channels but your is the one I like the most. Your explanations are straight to the point, very easy to follow as well as instructive. Keep the amazing work.
Great video! You didn't mention of a key point, I think... At least as far as the Class B/AB amplifier goes. If the Vbe multiplier is thermally coupled to the output transistors, then as they heat up and their Vbe drops, so does the that of Vbe of the Vbe multiplier transistor and the bias current through the output stage (and hence distortion) remains more or less constant through the operating temperature range. Also, it can help prevent thermal runaway...
Hola Alan! I finally subscribed to your channel. This last of yours, short and to the point, as usual. It allowed me to understand how it the multiplier works and what it is good for. You rank top in my list. Gracias.
ElectronicWizzard Thank you. Many people do not realize that every minute of published video can often represent 20-30 minutes of work - between preparation of materials, study, building, testing, note preparation, actual shooting of video clips, editing, etc.
***** Most people that think like that have never done anything. They think writing books are easy also because they have never tried to write one. I would estimate that you spent at least 5 hours on the video. Thanks for your efforts Alan - I greatly appreciate it!
Thank you for making EE videos to educate students and professionals And thank you for not doing old TV tear downs or how to use heat sink compound videos like the guy below the equator is doing.
Awesome video really helped clear alot of things up. I built the curve trace (octopus circuit) and followed along on my oscilloscope. works perfectly. really helpful.
I'm glad to come across your video on Vbe Multiplier. As I'm in the process of building a transistor stereo amp and in that, it uses a VBE Multiplier Power Regulator to regulate the power supply for the amp. I was wondering if there is a more up-to-date design to serve the same purpose or transistor amp should have transistor power regulator, thanks !
Without knowing specifically how the Vbe multiplier is being used, it would be difficult to recommend a different or more up-to-date design. If you're simply after a more up to date way to providing an adjustable voltage drop, then the most common modern solution would be something like the LM431. www.ti.com/lit/ds/symlink/lm431.pdf?ts=1644827857475
Absolutely love your circuit explanations. You have a real knack for taking all my unrelated knowledge about electronics and tying them all together. Please more circuit / discreet explanations. I found myself logging on just to see if you have any new videos. I have never did that before. Keep being bad ass. Thanks Also, just an idea, maybe you could make a video on ham radio and why it's interesting. I swear I don't get it. I go to hamfest but I go to buy electronic supply's and testing equipment. I just feel like I'm missing something because it seems like with my love for electronics i would be lured into it but man I got nothing. Zero interest and it bothers me immensely
Micheal Double Communication. If all other forms of communication are lost, Ham operators can still communicate and help people. My uncle John in Missouri was a Ham operator for a long time. He passed away a couple of years ago. I don't know what his call sign was though.
It would be difficult to encompass what makes ham radio interesting in a video - because every ham gets something different out of the hobby. Some like the challenge of making contacts with low power, some like building and using homemade equipment or antennas, some like playing with the latest technology, some like morse code, or using satellites, others like ragchewing with friends, etc. So, it all depends on where your interests lie.
Micheal Double I like Ham radio because it expands my interest in electronics into the realm of RF circuits (aka black magic and voodoo :o) ). It has also taken me into the realm of tube circuits which, believe it or not, are interesting. I found Alan's RU-vid Channel because of my search for how to use an oscilloscope for Ham radio. His ability to explain things in a simple and concise manner makes this site one of the top RU-vid channels for me.
Nice animated v-i curve of a variable diode. Are you going to show 4-quadrant V-I curves for MOSFETs and IGBTs in the upcoming video ? (in ON state and OFF state). There is a lot of confusion out there about the voltage drops and directionality of these components.
Allan, your videos are fantastic, thx. Tek even used some of your explanation methods at the SalesU this year. You have a great way of teaching things! If your not using the MDO3k memory stick please send it my way... Hahaha
Hmm - tell me what explanation methods they used (or what classes they were used in). I was at SalesU this year - bt only for the first two days. On Tuesday evening, I slipped on ice and broke my ankle and spend the next few days in the hospital before returning home.
Were you the one they mentioned about the broken ankle? Makes sense now, referring to your video about your broken ankle. Would have been nice to meet you and sorry for what happened. A couple of people fell and got hurt. I suffered so badly from jet lag, so I might be under correction. They obviously did give credit to you though, the one I specifically remembered was your way of explaining Res BW.
thank you so much for supplying all these so interesting videos, I spent a lot of time watching them the last weeks. For the moment I have one question: what is the name of this special mode that you use with your scope, when you display one channel versus the other (I vs V)? do you also use a current probe for measuring I while its channel is displayed in voltage units? I have a DPO scope but I don't think this feature is available on it, is it specific to the MDO serie? thanks again for your work which is very helpfull to me!
I am just using XY mode, and "measuring" current simply by measuring the voltage across a fixed resistor (the voltage will obviously be proportional to the current flowing through it). Your DPO should have XY mode.
@@frederichugenell5538 I didn't delete your comment. Apparently RU-vid blocks viewer comments that include links. So, I was able to copy your message from my email notification: w2aew thankk you for answering so quickly; and sorry for the so basic question I have asked, I know that oscilloscopes are supplied with this XY mode for a while, but I never used it; I have checked on my DPO and of course this mode is available; for displaying such a diode characteristic, I think you supply the circuit with a variable voltage (maybe a sine wave) between 0 and a few tenth of volts in order to be able to display the whole curve? and OK for probing the current with the resistor. I have another issue for which I want to ask your opinion: I'm trying to repair a bass amplifier for which the schematic is available on the web (cloud.univ-grenoble-alpes.fr/index.php/s/GeJYz6yGqEQwQqo), and I don't understand the biasing circuit of the push-pull output stage, it seems that the VBE multiplier is not biased symetricaly with respect to the rails (+/-V is around 30V), Q5 base is around 29.5V and Q6 around 28V, I don't understand how such a circuit is able to do the job, the positive swing will be very limited in such a case. Another question is the reason of the VBE multiplier fixed on the heatsink, I read somewhere that it should be thermaly coupled to the output transistor but I don't know the reason why. By advance thank you if you take time to answer me, and I you don't thank you nevertheless! Yes, I supplied the circuit with an AC voltage (waveshape is really isn't too important, but triangle works best, sinewave works very well too). With regard to your amplifier, there is definitely something wrong with your unit if you are seeing 29.5V at the base of Q5. As I look at the circuit, the base of Q5 should be about 1.5-2.0V above Ground, thus about 16.5 to 17V above the negative rail. I'm figuring this since the base of Q3 should be within about 100mV of ground, thus the base of Q5 should be a little over two Vbe's above that. The reason you want the Vbe Multiplier to the thermally coupled to the output devices is because the Vbe voltage is temperature dependent - it changes by about 2mV per degree Celcius. By thermally coupling them, the Vbe multiplier will more closely track the Vbe change of the push-pull devices over temperature.
@@w2aew thanks so much for giving me all these answers, you're really a great and nice person! I have to investigate deeply ni order to figure out and find where the issue comes from; I did some other measurement and I have 26V at the gate of Q3, but I don't understand the role of R97/R98/C60/C26 and why C26 is tied between R46 and R47. How do you deduce that Q3's gate is around 100mV with respect to the ground? thanks to you once again.
@@frederichugenell5538 I tried to go back to the schematic, but it looks like the file isn't available anymore, so I can't comment on the specific devices. A couple of general comments may help though. When figuring out the biasing point, any circuit branch that has a series capacitor can be ignored because it won't change the DC bias conditions with no signal present. For the front end which is a emitter coupled differential pair amplifier (as I recall), this type of amplifier has a practical working range for the differential input voltage of about +/-100mV. Once the input voltage difference goes beyond that, the amplifier output goes into limiting, provided there is no degeneration resistors in series with the emitters of the coupled pair. So, since the input is basically biased to ground via a 47k resistor, the other input (being fed via feedback from the output) must also be near this voltage in order for the amplifier to be in it's linear region. Other bias voltages can be estimated from this fact.
***** God bless your good work. There is always so much to learn from your videos and they are so easy to follow, that even a beginner like myself can udnerstand.
on timeline 5:01, where you showed the final equation to determine Vx, would it not be better then to place the variable pot between the base emitter instead between the base and collector? Otherwise if the pot between base collector opens up, you would have too much voltage driving the push pull amplifiers and the excessive current may burn the push pull amplifiers and may cause them to fail.
I wish I could wind my age back by 50 years, and still have your videos. Learning would have been so much easier. Unfortunately, I was taught by people that felt the need to show how clever they were at maths, leaving me lost. But, you do awesome demonstrations, with brilliant explanations. Thank you.
The way they teach students in college here in the US has been helping Asian countries to pass us. Companies like and promote that so they can have excuse to hire all foreign engineers and work them like slaves.
@@oakspines7171 You can rest assured knowing that while US students are learning about critical race theory, gender studies, blm, abcdefgq+, the Chinese students are learning Math, Science, Engineering. China will eat USA's lunch !
Very good lecture as always :) You can also use your beautiful oscilloscope (FFT function) to show how harmonic content changes with regulation and how it is connected with FFT function in our ears. Best Regards
That was great! Push-pull amplifiers biased with two standard diodes really cant compare to this method when using discrete components, but that's always the standard text book example of how to reduce cross-over distortion and never works well in practice I've found.
I love the way you explain! I've seen various videos on the subject and also about class AB amplifiers, but no one seems to think of playing a pure sine wave so that people can actually hear(12:20) how the distortion disappears with the bias change, and not just look at graphs.
Thanks again for great educational clip. I have seen this circuit on the push-pull Amps, but never understood it well. Now, I understand them well. I guess by extension we could do Vth Multipliers in MOSFETs. Thanks again for great Educational Clip.
Where is the button for 100 thumbs ups? Like Mick Healey below, you have in 13 minutes explained something that I totally missed when I was getting my EE degree. Then again, the $36,000 oscilloscope is helpful! :)
Very useful and very awesome indeed! The explanation and presentation are very clear and nicely interpretable, I like it! Awesome other videos on your channel aswell! You've earned yourself a new sub, keep up the work good man!
Thanks. I actually watched this video quite a while back, but I couldn't follow it at all. Now it makes complete sense. Although I understand Calculus well, which is not the same as doing derivatives and integrals, which really doesn't matter as much as understanding what it means. I have trouble following the math. I really guess that's a little bit of boredom, but I'll pull that in after a little bit. It's important to do at some point. I'm 53 now and thrilled to be getting back into electronics again. I did it very very young age and without hardly any money. Now I can actually buy some decent equipment. I'm starting to be able to use it, too. I'd enjoy using some good textbooks, but only with a group of people. Technical learning is a bit boring as DIY. Practical applied learning is fun now. Finally. Thanks again!
Totally love your videos. They should be shown at universities. You logically develop the ideas and everything makes sense. P.S.: Watching this video again and seeing that I've already commented, so I will edit this one. You need to publish a book where you can fold the pages as you do in your notes. It was fun as a kid and would still be :)
Great tutorial - sure wish RU-vid and teachers like you were around when I was learning electronics! I'll admit to skipping around a bit, so I might have missed this, but did you mention that another great thing about this circuit, particularly in the push-pull application, is that as Vbe changes with temperature, the multiplier's output will track the Vbe shift of the output transistors? So if you cancel the crossover distortion at one temp, it will stay cancelled as temp changes?
That's why in the classic Bailey Amp (from 1968), the bias transistor is mounted onto the same heatsink, close to the output transistors, to ensure thermal tracking. Do a search on the web for "30-watt High Fidelity Amplifier" if you're interested in reading a full description of the amplifier. I built one of these over 50 years ago and I've still never heard anything sound better.
Thanks, I thought this would be a disadvantage. As the junction voltage easily changes by a factor of two it is really a terrible idea to use it as a reference unless that is exactly what you want for compensation.
Very nice demo, thanks for making it. I always enjoy your tutorials, both the drawn circuits and then the demo on test equipment. Very real stuff. Thanks.
In my amplifier output stages I use to couple the transistor of the Vbe multiplier thermally with the output stage and I use a constant current source (f.i. E-103) instead of Rc. In this way you can get a very stable bias current through the output stage.
Before watching this video, I was aware of Vbe multiplier circuits -- thanks to a coworker. However, I was NOT aware of the push-pull output application! That is brilliant!
I work with these "Push Pull" everyday service electron microscopes. All the scan circuits utilize a push-pull circuit. I remember learning about the PUSH-PULL circuit in college, but never fully understood how to compensate for the crossover distortion until NOW! Your videos/ instruction is "Priceless" and should be required viewing for any electrical engineer student!
Thanks for all of your videos! I am currently expanding my electronics knowledge by troubleshooting a Fender M80 bass amp, which has distortion at the output, and this sheds some light, hopefully.
Seems to me that this circuit would be applicable to an analog map sensor in a car. Take the sensor output and shift it down? A simple voltage divider with two resistors between signal and ground works well but ot does put extra load on the sensor output. (Diode doesn't it actually shifts it up as it goes to CPU that has short circuit and open sensing).
Thank You for Your really informative and enlightening videos. I now have an understanding of Vbe Multipliers and also what cross-over distortion is. I see that another 'aka' for this circuit is a 'Rubber Diode' according to Wikipedia.
I DO like your videos Alan but in this case I have always used 2 diodes in series to eliminate the cross over distortion of an Audio output stage. I'm sure though there are other uses for this circuit and the example is used as an alternative method to eliminate distortion, and here of course you have more control.
You obviously put a significant amount of preparation into your videos and your command of the subject is obvious. The result is a professional and easy to understand lesson. . Much appreciated!
this looks like a very fundamental building block, that I have not seen before. I suspect it can replace zeners as well for introducing arbitrary voltage drops.
