TSP #23 - Tutorial on the Design and Characterization of Class-B and AB Amplifiers 

*Please note that in the schematic diagram the diode D1 is backwards! In the measured circuit the diode is placed correctly which is why the measurement results are correct.*

You have no idea how long I've been looking for some kind of tutorial on amplifiers that doesn't just mathematically develop the small signal model. Thank you kindly, and to boot, it's super straightforward and clearly explained.

This video and TSP #15 are the best intro into audio amplifier design I've seen. Many college electronics Subjects fail to explain it so simple.

How come have I never seen this! This is a great "must watch" video and, despite its age, should be recommended by RU-vid.

You are a better teacher than all of my profs combined, you make concepts so easy to understand and more importantly you make it fun because you're just an awesome dude. I wish you the best in these trying times.

I appreciate your enthusiasm. I am trying to cover a wide audience. Don't worry, there are tutorials on DSB and SSB mixers and complex constellations for wireless transmission which will target a more advanced audience.

This is a conceptual schematic diagram. Both diodes D1 and D2 require a bias current to maintain their junction voltage. But, perhaps more importantly for you to consider, my channel has received about 1300 comments so far. You are the first to use obscene language. My channel is a place to exchange information politely and I would like to keep it that way.

The answer of the puzzle: You have clipping, your input signal exceeds the supply voltage

That was the best and clearest explanation of class B amplification I have ever seen

Class-D is a good option. I may do a tutorial on that later.

Very nice short tutorial. 👍 I also see that here, 11 years ago, you have significantly less equipment compared to now 😁 Keep up the good work!

WOW! What a great tutorial - very clearly explained, spot-on comparisons of the different amplifier designs, and beautiful hands-on lab experiments to demonstrate relative performance. And what a neat and organized lab you have!! Thank you so much!! Can't wait to dive in the the many, many other videos you have published.

Thank you very much! Very clear, I'm going to be digging around your videos all night now.

Just want to state my appreciation to you developing these videos. It is a great way to learn (or review in this case) electronics material. Keep it up!

Thank you for this clear tutorial and refresher for me. I am jealous of your collection of test equipment!

Very good video. The tutorial was not overwhelming. A perfect mix of theory and practical hands on visual elements to glue it all together. Thanks for your work.

I was just curious about A and AB amplifiers because I play electric guitar and I found this video. It was still fun to see the explanation and the experiment. Thanks.

The way you taught this is just very simple and straight forward, I am mech engineer looking to build my own class ab amp for gaming in my home! Learnt many things, Ty!

Great tutorial! your D1 is oriented incorrectly and signal needs to be applied to each base of the transistors and not to the middle of the diode network. Adding some input caps to kill any dc is a good practice. Also, consider using a Vbe multiplier for the a-ab amplifier. It saves you a transistor plus you can use a potentiometer to dial in the biasing current.

Another awesome shot my friend, specially when it comes to measuring. Good stuff around there... THANKS a lot for sharing your knowledge and the way you explain it. BLESS 🎩🙏🏾...!!!

An outstanding and comprehensive tutorial on amplifiers. Thank you so much.

I can't commend you enough for putting these videos together. They're tremendously helpful for somebody like myself - trained as a scientist many years ago - rediscovering the joys of electronics. Thanks, and best wishes!

just learned more in 39 minute video then in 16 weeks of advanced electronics taught by some old fart with no clue Awesome video Thank you

I really loved this tutorial. You have a great way of explaining electronic circuits. Keep up the good work.

Thank you man for the video! This is the best explanation what I ever see. I am not professional and I sow so many videos trying to understand the bias and the class of amplifiers.. Thanks to you know finally understand a lot!. Thank you ! You just have big talent to be a good teacher! God bless you !

great video! very informative, no BS, visual representations are good, well explained and to the point. A+

Wow, you answered so many questions I had about the interaction of input impedance, the buffer, and preamplifier stage of an amplifier design. Thank you. (liked/subscribed) -Jake

Thank you for taking the time to make this exceptional tutorial.

Thank you so much for these videos, helping me through my University course. I didn't even know what a spectrum analyzer did before watching this. Now I want one!

These are great videos by the way. Honestly, one of the best channels on RU-vid. Please keep making these great videos!

Many thanks for the explanation, Shahriar, absolutely clarifying!!!

What a fantastic video! The way it's put together makes it very easy to follow and a joy to watch.

Excellent resource for someone graduating from class A understanding into class B (like me). Thanks for posting this

Im liking the video just by reading the title and knowing the level of detail you go in to!

Great work! Comprehensive and easy to understand! Subscribed.

He talks about turning off the bias voltage when the input equals zero. -- Great video! I really liked it! Made me happy about the next few months of studying :)

This is a very old video! But a very good old one! Thank to God of Science that my 'luck' is good! This is the best ever 'tutorial' on amplifiers! Shahriar's A + AB design actually works and works frighteningly well! I mean, I simulate it. I have nearly zero hope that simulators (I use Multisim) are accurate, let alone precise, but when I match those measured and simulated numbers they are frighteningly similar! I say this because (simulated) component data are far from realistic. I do not mean the intricacies such as temperature, vibration, and so forth. I actually mean basic characteristics such as saturation, breakdown, and so on. Most op-amp, for instance, have zero limitation, you can feed them kilo volts input and kilovolts of power supply and the the output signal still looks normal! Same goes for diodes. I now wonder how to actually make it an amplifier, which component to change. The circuit is not exactly an amplifier but a current/voltage follower. There is no amplification.

I really wanted to hear some audio through each! Great video as always.

awesome video, shahriar...keep up the good work.. answer to the quiz is "with increasing input voltage u r saturating the transistors gradually that's y output is getting clipped off. after all you'll never get output higher than the driving supply voltage.."

!0 years later and I answered some of your students to say they were correct Lol ! still pure gold....cheers.

This is a really great tutorial Shahriar! Thank you so much!)

Absolute pleasure learning from you!! Great job!!!!!!!!

Congratulations, your explanation is brilliant. Thank you for sharing!

I see some very good comments below. Early in the video the dead spot is caused voltage consumption called (Diode Drop). For the "Question" I agree with the comments bellow. Supply voltage, headroom, saturation, and gain. Very good information. Very well made and thought out. Feel like part of the class. Thank you!

Yes, much appreciated. I added a note to the video.

hats off for giving such a good and long explanation in a single take!

Yes, they come with the scope as part of the probe package.

Another excellent video! Once again, I appreciate all of your hard work. Very high quality instruction. I believe the answer to your quiz question is the distortion is caused because you are using 2.5 volt supplies. The distortion is caused because there is not enough voltage to drive the transistors through the complete cycle. The transistors are clipping the input signal when they are saturated.

Thank you, my friend, Shahriar you saved a lot of time for me

Excellent video!!! Thank -you for sharing your knowledge.

You deserve more subscriber friend, and I wonder what kind of person are those who disliked this video, its one of the best tutorial explained & demonstrated in details! Thank you for share your video and knowledge.

big thanks for making this video, really helpful!

i don't know how to appreciate to your time and effort to do this tutorial for us

About that puzzle... it seems that the higher the input level, the closer the emitter potential of Q1 gets to V+, so less current is available to go into the base of Q3 and so the output levels off, falling behind the rise in input potential. Love your videos by the way, the topics, the format, the explanations, everything. Thanks a lot for making them.

Thank for the excellent video presentation. First explaining the theory of various classes of amplifiers and demonstrating their workings on the oscilloscope gave a very good idea of their positive and negative characteristics. Please make a video on how to design a working amplifier, explaining how to calculate and choose parameters of various components. With such knowledge, as yours, you can write books for hobbyists and professionals. We need more videos like this.

Thank you for explaining this so well. Much appreciated

Brilliant, absolutely loved it! Much better than my teacher...

Thank you very much for the video. Your lecture is very clear and well done!

Good video and well explained. My guess for the part near the end of the video is the input signal becoming to strong driving the transistors into saturation, but I could be wrong. Right now I'm actually listening to this through a valve amplifier I made!

چون تقویت کننده شما در اون ناحیه به اشباع میرفت.تشکر بابت مطالب اموزندتون

That was great! Thank you Shahriar.

Good job, clear concise easy to follow!

Great stuff. Look for more. Thank you.

Shahriar, Very good videos, I wish I had instruction like this in high school "Electronics I" instead of electron hole theory in the early 80's. Not many high schoolers back then were designing semiconductors. I like you very practical theory and demonstration techniques in all your videos, especially the analog circuits Thanks very much!!!

Really good explanation! Thanks for the class.

I remember this from when I took my amateur radio tests.... 15-20 years ago.... but never have actually seen it real-life. Very cool.

Very thorough and to the point...thanks!

I have recently discovered your tutorial in the internet they are all very informative thank you for taking time to explain complex electronic concept all so very nicely I am very thankful. My answer to your quiz question at the end of the video about the non-linearity region of the signal is; I think the bandwidth limitation of the transistors in the circuit.

whoa..im amazed with all those gears you have there

You are awesome teacher! Thousand times better than all my high school el. teachers. Not to mention I have to translate from english. Your 'lucky bamboo' is larger than the last video.

This is pure gold...cheers.

You are right. This is a simplified diagram. I have added a note the video to clarify that.

holy cow with all those equipment's. you have more stuff than what I have in my bench at work

Great series! The amp looks bare without negative feedback though!

I'm guessing you were a great TA as a PhD candidate...wish you were around when I was an undergrad (though, you probably weren't yet born) ;). You teach with great clarity and enthusiasm and remind me why I was so excited to become an EE...which is really uplifting in my, ahem, older years.

CHEERS MATE GREAT ONE. Significantly helpful. If you could have some thing similar on class D, would be great.

Great video. Thank you very much for the excellent explanation

Excellent tutorial....thanks. Off to try this for myself!

Wonderful tutorial. excellent presentation and very clear...Thanks...

Very educational. college was fun. I could have learned more if we had enough equipment for everyone in the class to experiment with.

You need a small current flow through D1 and D2. and one of the diodes is backward. I have added a note to the video.

OMG I have been looking for a video like this for sooooo long!!!!!

Great presentation. The answers to the question are listed below. Keep these wonderful videos coming.

Great video!! All the best congratulations!!:)

Another great video! Thanks.

excellent usage of electronic language, clearly understood.

Extremely informative.Thank you very much!

this video is absolutely fantastic. brilliant, really.

Love this kind of video! Educational and practical, a perfect learning tool. And it's been answers, but your input is exceeding the rails on the output, so you are clipping, in freq domain you would see flats at the top and bottom of the waveform. At least that's my guess.

wonderfully explained, thanks :)

Very informative, keep it up.thanks a lot

very good explanation.. your lab well organized,

Thank you for this. Best explanation ever

The spectrum analyzer can have up to 30VDC at its input without damage. That is because it is AC coupled. Furthermore, it can see up to 30dBm of input power which I could not generate.

The spectrum analyzer is AC coupled at its input. Furthermore, the output load of the amplifier is 10Ohms. Therefore, adding another 50Ohm in parallel has minimal impact.

Cheers, really clear explanation.

you have wonderful resources and equipment. taking the time to explain each class and showing the effects on the oscope are priceless time savers for us learning. thankyou so much

Its a very good explanation... helped me alot... Thank you so much

Superb video, very well explained as always.

Thanks Shahriar. Thumbs up!