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

[@Thesignalpath]

*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.*

[@ve2um]

Also, in the X-Y scope, Y is input and X, output.

[@7137271]

I thought that looked funny, and kept trying to figure out how that was going to work.

[@andr27]

Video posted 8y ago and only 10 months ago errata? :)

[@SJayanth]

The reason for no output at 5v p-p input I think is because the current through the first stage of transistors went too high and the gate voltages for the next stage of transistors fell below 0.6, thus, there was no output. Anyway, we started to build amplifiers right? but, neither of the 2 designs could output a voltage higher than the input, then, how can we call these as amplifiers? Please, reply quickly. And thanks for the video.

[@VolodymyrTorkalo]

@@SJayanth It amplifies current. Before it you need add stages which amplify voltage - in common emitter configuration.

[@WhiskeyRichard.]

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.

[@WhiskeyRichard.]

Why doesn't this guy prof Oh wait stupid question

[@jonothankaplan]

@@WhiskeyRichard. hi

[@Hexor1211]

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.

[@bloguetronica]

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

[@jonramsey6348]

Yea totally..... finding this video on KZbin is like finding a diamond in a pile of shattered glass

[@neeleshkumar8406]

Same here ,

[@graemelaubach3106]

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.

[@Thesignalpath]

Thank you!

[@omniyambot9876]

wholesome comment lol agree 0:09

[@Thesignalpath]

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.

[@AltayBrusan]

Thanks for your sharing. I am really disappointed with those that do not consider the value of these videos for the others. thanks and please don't loss your motivation. Your channel is valuable.

[@Thesignalpath]

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.

[@thebrakshow7415]

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.

I just wanted to write this as well. In Class AB amplifier diode orientation is wrong.

[@simoncheung2427]

i can’t believe after i watch a whole video and looks everything make sense

[@m1geo]

Just came to write this! 😂

[@BobSolimeno]

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.

[@bassk94]

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

[@serviceshoptoday]

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!

[@relaxationTherapy001]

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.."

[@CmAektP2jxrGAb7]

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.

[@Thesignalpath]

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

[@johnadams9041]

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 !

[@sudharsansuresh170]

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!

[@wombatau]

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

[@chupascz]

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.

[@peep39]

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

[@VLWhite88]

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

[@andymouse]

Correct ! no prize now though Lol ! 10 years later !

[@generatorlabs]

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.

[@raulvalenzuela4887]

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.

[@rcleveacp]

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.

[@einball]

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 :)

[@MrAtomicLlama]

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!

[@MarysKiril]

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.

[@andymouse]

And 10 years later...The signal is clipping and your correct ! unfortunately you have no prize !

[@andymouse]

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

[@vispi1944]

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.

[@MBAgeeJr68]

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

[@ernestb.2377]

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!

[@jimshaw4424]

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

[@MinnoW12]

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

[@DarkInsanePyro]

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!

[@dataviews118]

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

[@LolanBadeauxMakes]

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

[@n1gdawg]

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

[@antoniocastrocarballal4051]

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

[@UpcycleElectronics]

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

[@SamWalsh1]

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!

[@Hanz_theengine]

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

[@raviduprasanna6401]

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

[@permitivitym4318]

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

[@permitivitym4318]

that's a $10,000 scope

[@LolanBadeauxMakes]

yes he has an awesome bench setup. i so jelly =)

[@alicekichlu215]

I AGREE!

[@realchristopher4334]

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.

[@jimm2099]

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!!!

[@zaroaster8348]

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.

[@eduardorubin7661]

You just saved my thesis. Thank you!!

[@4833504F]

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

[@x86cowboy]

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

[@DanielFries]

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

[@FFcossag]

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

[@CoolDudeClem]

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!

[@jtb8631]

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

[@nazanwar6469]

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

[@stever128]

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

[@Thesignalpath]

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.

[@rossrogers2979]

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

[@Hexor1211]

Puzzle for the Day (36:30) - We are looking at amplifier going to saturation (clipping). Input signal is to large and output transistors are in saturation region (collector current changes little or none versus base current). We can see that one transistor (negative swing) goes into saturation before the other transistor.

[@SJayanth]

The reason for no output at 5v p-p input I think is because the current through the first stage of transistors went too high and the gate voltages for the next stage of transistors fell below 0.6, thus, there was no output. Anyway, we started to build amplifiers right? but, neither of the 2 designs could output a voltage higher than the input, then, how can we call these as amplifiers? Please, reply quickly. And thanks for the video.

[@todkapuz]

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.

[@octavmandru9219]

Clipping due to the 2.5V limit of the power supply. Love your videos, don't care how old they are

[@weststarr2046]

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 🎩🙏🏾...!!!

[@castimann]

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

[@simonyoungglostog]

I love how you think. It's very helpful for me to hear you think out loud. I have a question about using a PNP with a NPN to match a voltage drop? I hope that makes sense..

[@zohirbailiche7322]

Dude.... The diode you were pointing at at 11:17 is in wrong direction... Doen't it?🤔

[@lukesnake123]

this video is absolutely fantastic. brilliant, really.

[@zianadir]

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

[@saviourslumber]

Great work! Comprehensive and easy to understand! Subscribed.

[@RobertGallop]

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.

[@mbabaeevideos]

Thanks Shahriar. But you've placed the top diode D1 in the first AB amplifier schematics in revere polarity.

[@musicmakelightning]

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.

[@michaelpukmel9175]

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

[@paulrajmarichamy4309]

very good explanation.. your lab well organized,

[@Thesignalpath]

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.

[@alextrofimov7947]

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

This was a great video! Are you planning on making videos about other amplifier types as well? That would be great!

[@Thesignalpath]

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

[@s.r.m.m8789]

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

[@Standing-Wave]

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

[@martinda7446]

Just a minor point, the distortion is called 'crossover distortion' and the history of manufacturers to overcome this and other areas of harmonic distortion is fascinating with the THD wars and giving us 0.0001% thd and below. 0.1% is considered ideal and was given us first by H J leak in his ''point one'' amp series in around 1948 (from memory)

[@TheLawnWanderer]

+mart fart push-pull ultra linear valve amplifiers are no joke. The circuit family is called Williamson amplifiers.

[@martinda7446]

TheLawnWanderer Leak predated the Williamson and I dont beleive it was ultra linear design I think williamson used ''overall'' negative feedback as a first and envisaged a triode output not pentode/tetrode. Blumlein invented ultralinear in the 30s along with many other great discoveries.

[@TheLawnWanderer]

mart fart point one wasn't UL, but triode connected instead. The later ones were UL though, really no point to not use UL. Pretty much all modern amplifiers in that style are UL with the option to switch to triode with a simple switch.

[@Lowracerman]

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

[@camelazo]

Hello community i have a silly question , why in the amplifier A+AB the amplified signal ( in blue) is less Vpp than the input source? (yellow one), Regards. 35:16

[@yxk081]

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

[@horaciohherasq6526]

Do you always need a dual power supply to power an AB amplifier? I'm a newby at building these amps and your lessons are pure gold.

[@Popart-xh2fd]

11:25 In the Class AB amp scheme with the diodes, the voltage offset I got between transistor bases was 1.0V instead the expected 1.2V (0.6 + 0.6). Nevertheless I got no distortion on the output! The XY graph of the sine wave of each transistor base is a straight line that intersects the XY axes on 1V and -1V respectively! Why not 1.2V as expected?

[@toryvaughan4940]

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

[@Thesignalpath]

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

[@freeelectron8261]

The non linearity we see at the ends of the XY plot (36:30) are due to the sine peaks going beyond the supply rail voltages, so the amplifier cuts off the peak curves and a flat top waveform results.

[@doctorbo5810]

Great video. Thank you very much for the excellent explanation

[@roylumsden1017]

excellent usage of electronic language, clearly understood.

[@213pool]

Insightful and inspiring. Thanks for sharing

[@Thesignalpath]

Glad you enjoyed it!

[@Thesignalpath]

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.

[@_a.z]

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

[@himanandini2161]

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

[@DeltaSigma16]

at 36:22 the push pull transistors are going to saturation, that why the input and output do no longer have a linear relationship ! Saturation here means litteraly no matter how high the input get, the output don't change.

[@taz0k2]

I don't see the reason why the 1k resistors are needed at 19:56 . I know that a single transistor has to be biased in order to "let through" both plus and minus of the incoming signal. But isn't adding a bias of 0V like not adding any bias at all. I mean zero is nothing, x + 0 = x? The capacitor is (already) making sure that only AC is coming in?

[@lonewanderer01]

So is it that you've reached saturation in the transistor?

[@ve2um]

Saturatio will be reached if the input signal (peak) reaches the NPN' collector's voltage + 0.6 volt (an PNP collector -Vcc + -0.6V). In the deadzone, both transistors are in cutoff region.

[@miguellorenzo3726]

Hey, excellent video, you kept my attention during 40 minutes which is quite an achievement :D

[@rickysambora8321]

Nice equipment there. May i know the drill stand that you got there (or something similar, I guess yours it's no longer stocked)? i have a similar drill too like yours.

[@hasan0770816268]

big thanks for making this video, really helpful!

[@davidcottrell1308]

Very thorough and to the point...thanks!