Hello M. Jellouli. This is the clearest and most engaging video on the subject that I have seen. Thank you so much. I am sure your students enjoy your lectures greatly. Regards.
So much easily and cooled explained. Its help me so much.so my concept is clear about this which i couldnt do with my text books. Thanks a lot. We want more and more tutorial from you.
I am thinking about adding more tutorials about some electronics concepts. Stay tuned. I definitely have more time now and I will be able to produce more videos in the near future.
Thanks for the video, Need to put something in mind and make it clear for all is that. The efficiency of Class A is 25% and Class B is 78.5%. there is huge gap between 78.5 and 50%...
good explanation, but we learned(proved) in our electronics class that class B has an efficiency of around 78.5% (pi/4) for a sine input Pccp(t)={Vcc*ic1, 0
How about R1 and R2? Did you include those in your calculations along with the current flowing through them at all times whether there is an input signal or not? Did you also consider the more common case when there is a coupling capacitor in front of the load resistor? That would allow only AC current to flow through it. This simple addition would make all your calculations incorrect. I might do another video covering the power calculations. I can guarantee you that your 78% is way more than one could hope to get from a class B amplifier. You have dealt with extremely simple cases that would not work in a real circuit.
excellent video !! but, i didn't understand in one part. time: 21:53 :: as the ac signal rises from 0V (increase in positive half) , how does the base current flow in T1. The diode D1 will be in reverse biased and it don't allow the signal to pass through. So, what happens in this case ??
D1 is ALWAYS forward biased. its purpose is to raise Vbe of T1 to get 0.7 V so that it conducts. it is never ever reverse biased. The same applies to D2.
Thank you very much for this explanation, Just need some clarification about class B amp: doesn't the 0.7V come from Vs+ and Vs- or they cancel each other?
How do you explain that the class B amplifier does not conduct when Vi=0? Shouldn't the Vcc power the transistor with a Ib, like it happens with the class A? You mentioned that all the current goes through R1 and R2... but why?
Good explanation, however my question is class AB design although it eliminates the distortion, it brings back the problem we had in class A. Your T1 is on when input is zero so how is it better?
+thetruereality Not really. There is no DC current flowing through the transistors because when one is on, the other is off. There is also no DC current flowing through load resistor because of the capacitor. Now when there is an AC signal at the input, there will be an AC current flowing through the load resistor.\ So all in all, it has the same merits as the class A, but the efficiency is increased by at least a factor of 2.5.
thetruereality It is not the same at all. T1, or T2, conducts ONLY when there is an input. Thus no waste of power when there is no signal at the input. Notice however that both diodes are always on. However by choosing large values for R1 and R2 we keep these losses at a minimum.
@@SaadouneZinji In order to have only one transistor on and the other off, we must tolerate some degree of distortion correct? Also, the DC voltage between D1 and D2 should be the same as Ve, perhaps Vcc/2?
This video is helpful. how can you help in the case where i repaired class AB amplifier, during testing process the amp blows output transistor once input signal is increased. Besides that, what should i measure to ensure that a biasing circuit output voltage and current are optimum for a pre-amp transistors. Thank you
I know it is just an abstract, but why if the max efficiency is 30% would you show Ic going to zero on a Ic/Vce curve @4:30? I learned this before but in pieces.
Mr. Kumar is correct. Voltage gain is typically achieved in the Class-A pre-amp section(s). The Power Amp section is designed for current, not voltage. It takes current to run the motor in a speaker in order to move the air.
Class A isn't just "On" at all times, it's running at FULL POWER OUTPUT at all times, even without a signal in, causing high heat conditions & low efficiency.
Great video. With the class B amp, why is there a route that pulls positive voltage behind the two transistors across R1 and R2? What does this part of the circuit do and why do we need it?
Hey thanks for the video. Just a quick question about the design of the of the Class AB amplifier. How do i find the values of the two resistors and the capacitors. I have found the KVL around the Resistor and the diodes, which is; R = (Vcc - 1.4V)/(2*I) . But i dont know what to put for the current in the KVL. Also, my load resistor is 8 Ohms. Thanks you
I recognize the voice. Hello again professor, great job on the explanation... I didn't know you understood the amplifier so well. Please contact me at your earliest. Thank you!
WHY we need the resistor r1 and r2?????and why the transistor will not on as we have Vs onnected ,,it can take voltage from there!!why ont it be on "on" state??
Perchance I was doing a little research on amplifiers and just so happened to run across a very familiar name of Said Jellouli. I wasn't so sure at first, but when I navigated to your youtube channel and watched some of your other videos, there was NO mistaking from your voice that you are the one and only Professor Said Jellouli from Devry University - Chicago on Campbell Ave. ALHUMDULLILAH! The only professor I ever saw who could lecture without notes or a textbook and pick up at the exact same place that you left off from the previous lecture of a week ago. Assallamu Alaikum!!! Devry University Allumni 2005 EET Graduate. Are you still teaching there or are you at a different location? Hope that all is well with you, Inshallah!
The class ab amplifier has a conducting path for v=0 ,then how is it differing from a class a amplifier. I meant that transistors are involved when diodes are forward biased and the diodes are forward biased even if vin =0.
Excellent explanation I understood about 70% of your lecture. What I didn't understand is the circuit diagram of specially class B and Class AB. You didn't discuss that circuit diagrams in detail. I mean What is the purpose of the applying +V voltage and -V voltage and whats the purpose of R1 and R2?
V+ is the activator for the npn transistor (Ic will from v+ to load (0) in npn.) V- is the activator for pnp transistor (Ic will from load (0) to v- in npn.)
Yeah mate, easy enough to draw a ocl class a amplifier working in common collector configue. You know how to make one thats class a and works in common emitter ? which is ocl? I bet you don't
Hello M. Jellouli. This is the clearest and most engaging video on the subject that I have seen. Thank you so much. I am sure your students enjoy your lectures greatly. Regards.
efficiency of class A amplifier is 25%
efficiency of class A transformer coupled amplifier is 50%
efficiency of class B amplifier is 78.5%
Efficiency can't be exact. It may be about those values.
what is the efficiency of class ab amplifier
Didn't knew Morgan Freeman has a Electronics degree
So much easily and cooled explained. Its help me so much.so my concept is clear about this which i couldnt do with my text books. Thanks a lot. We want more and more tutorial from you.
I am thinking about adding more tutorials about some electronics concepts.
Stay tuned. I definitely have more time now and I will be able to produce more videos in the near future.
Superbly explained. Love the blackboard style drawing tool also !!1
Thank you so much for this video! Helped me out a lot
Thank you so much for the tutorial! It really helped me out.
Thank you, Said, fine lecture, very clear.
Thanks for the video, Need to put something in mind and make it clear for all is that. The efficiency of Class A is 25% and Class B is 78.5%. there is huge gap between 78.5 and 50%...
Well explained.The kind of tutorials i was looking for!
Thanks so much! Make more videos! You explain things very clearly!
You are most welcome!
Extremely helpful!! Thank you so much
Good explanation mate. Much appreciated..
Thank you so much sir, it's good explanation and thank to showing us current flow, thank you so much sir
Very well explained. Thank you so much for the tutorial...
you sound like denzel washington
You explained so clearly , thank you so much , nice tutorial sir.
Thank you.Very good explanation.
good explanation, but we learned(proved) in our electronics class that class B has an efficiency of around 78.5% (pi/4) for a sine input
Pccp(t)={Vcc*ic1, 0
How about R1 and R2? Did you include those in your calculations along with the current flowing through them at all times whether there is an input signal or not?
Did you also consider the more common case when there is a coupling capacitor in front of the load resistor? That would allow only AC current to flow through it. This simple addition would make all your calculations incorrect.
I might do another video covering the power calculations. I can guarantee you that your 78% is way more than one could hope to get from a class B amplifier. You have dealt with extremely simple cases that would not work in a real circuit.
you are right, we ignore R1 and R2 and the coupling capacitors
excellent video !!
but, i didn't understand in one part.
time: 21:53 :: as the ac signal rises from 0V (increase in positive half) , how does the base current flow in T1. The diode D1 will be in reverse biased and it don't allow the signal to pass through. So, what happens in this case ??
D1 is ALWAYS forward biased. its purpose is to raise Vbe of T1 to get 0.7 V so that it conducts. it is never ever reverse biased.
The same applies to D2.
thank you so much..!!
i was trying this from 3 months,
you made my day.. :D
+shreeya nagar I am glad this was helpful. I was just trying my new tablet and decided to make this video about class A, B and AB amplifiers.
@@SaadouneZinji thug life
VERY informative video, thanks for sharing !
Very Nice
How the positive input voltage forward bias transistor 1 having reversed bias of the upper diode ?
I think he is explaining well but the diagram is wrong.The upper diode should be foreward biased
Thank you very much for this explanation,
Just need some clarification about class B amp:
doesn't the 0.7V come from Vs+ and Vs- or they cancel each other?
Really awesome lecture.
can u tell us more about class d amplifier like this one
thanks sir
very well explained. I just need more explanation on how does the diode bias works.
excellent, well explained , so clear
Excellent work sir !!!!
What is the equation for class B & AB amplifier efficiency?
awsm video👌👌.... make some more stuff on electonics & engg. related topics ......
I think the class B amplifier won't have the two resistors (R1,2)
AS they would result in current irrespective of the input signal.
How do you explain that the class B amplifier does not conduct when Vi=0? Shouldn't the Vcc power the transistor with a Ib, like it happens with the class A? You mentioned that all the current goes through R1 and R2... but why?
Good explanation, however my question is class AB design although it eliminates the distortion, it brings back the problem we had in class A. Your T1 is on when input is zero so how is it better?
+thetruereality Not really. There is no DC current flowing through the transistors because when one is on, the other is off. There is also no DC current flowing through load resistor because of the capacitor. Now when there is an AC signal at the input, there will be an AC current flowing through the load resistor.\
So all in all, it has the same merits as the class A, but the efficiency is increased by at least a factor of 2.5.
thetruereality the standby current in class AB is miliamps.....in class A, this could be low amps dependent on design...much less efficient
thetruereality It is not the same at all. T1, or T2, conducts ONLY when there is an input. Thus no waste of power when there is no signal at the input.
Notice however that both diodes are always on. However by choosing large values for R1 and R2 we keep these losses at a minimum.
@@SaadouneZinji In order to have only one transistor on and the other off, we must tolerate some degree of distortion correct? Also, the DC voltage between D1 and D2 should be the same as Ve, perhaps Vcc/2?
I love this explaination
This video is helpful. how can you help in the case where i repaired class AB amplifier, during testing process the amp blows output transistor once input signal is increased. Besides that, what should i measure to ensure that a biasing circuit output voltage and current are optimum for a pre-amp transistors.
Thank you
What is the minimum value of the DC biasing current in class A output stage?Explain you answer
What reference are you using when you say .7v at the base?
Hello could you tell me what software you use for your pen. I like your penmanship
I know it is just an abstract, but why if the max efficiency is 30% would you show Ic going to zero on a Ic/Vce curve @4:30? I learned this before but in pieces.
Awsome explanation
an amplifier is meant to amplify the signals .But in here if the output just follows the input then how is amplification possible.
Mr. Kumar is correct. Voltage gain is typically achieved in the Class-A pre-amp section(s). The Power Amp section is designed for current, not voltage. It takes current to run the motor in a speaker in order to move the air.
Very Nice Video.
Great video, thanks very much
for the Class AB amp. what is a typical DC current that this driver can produce? How much current needed to drive 8ohm speaker?
Class A isn't just "On" at all times, it's running at FULL POWER OUTPUT at all times, even without a signal in, causing high heat conditions & low efficiency.
I don't recall saying otherwise!
So why in case of Class A the transistor conducts for both cycles even though negative cycle cannot turn the transistor ON?
Great video. With the class B amp, why is there a route that pulls positive voltage behind the two transistors across R1 and R2? What does this part of the circuit do and why do we need it?
Peter Short Their job is to bias the diodes D1 and D2 to make up for the 0.7 V needed to turn on the 2 transistors.
said jellouli but there are no diodes in the class B?
Indeed there aren't. Those resistors are there to bias the transistors.
ah ok :) cool
Hey thanks for the video.
Just a quick question about the design of the of the Class AB amplifier. How do i find the values of the two resistors and the capacitors. I have found the KVL around the Resistor and the diodes, which is; R = (Vcc - 1.4V)/(2*I) . But i dont know what to put for the current in the KVL. Also, my load resistor is 8 Ohms. Thanks you
great lecture sir
I recognize the voice. Hello again professor, great job on the explanation... I didn't know you understood the amplifier so well. Please contact me at your earliest. Thank you!
pls tell the method of selecting and calculating the values of resistor ..
how can calculate the efficiency ?
Really artistic writing
awesome video!!
Great explanation but do you have any examples on the derivations?
Can i know, what happen to class a and class b if i keep on increasing the dc/ac voltage?
lacks explanation in class AB when negative input given.....remaining good
how come this video falls in category comedy ?
btw awesome explanation...
I like the way you explain. Your writing at the end is a little bit a mess but it's ok.
Thanx
You are awesome !
Is class A amplifier and class A push pull same thing?
24:40 as it current flows through RL the assumption about zero volts made on 23:00 can't be true. It's should be current times RL. What did i miss?
The transistor is half on till sig comes along...
WHY we need the resistor r1 and r2?????and why the transistor will not on as we have Vs onnected ,,it can take voltage from there!!why ont it be on "on" state??
Perchance I was doing a little research on amplifiers and just so happened to run across a very familiar name of Said Jellouli. I wasn't so sure at first, but when I navigated to your youtube channel and watched some of your other videos, there was NO mistaking from your voice that you are the one and only Professor Said Jellouli from Devry University - Chicago on Campbell Ave. ALHUMDULLILAH! The only professor I ever saw who could lecture without notes or a textbook and pick up at the exact same place that you left off from the previous lecture of a week ago. Assallamu Alaikum!!! Devry University Allumni 2005 EET Graduate. Are you still teaching there or are you at a different location? Hope that all is well with you, Inshallah!
ks ks Hi brother! I am now mostly at the Tinley Park campus and at times at the Addison campus!
Who are you?
Brilliant !
WTF, u have a very good hand writing in letter V
The class ab amplifier has a conducting path for v=0 ,then how is it differing from a class a amplifier. I meant that transistors are involved when diodes are forward biased and the diodes are forward biased even if vin =0.
💗💗💛💛
Excellent explanation I understood about 70% of your lecture. What I didn't understand is the circuit diagram of specially class B and Class AB. You didn't discuss that circuit diagrams in detail. I mean What is the purpose of the applying +V voltage and -V voltage and whats the purpose of R1 and R2?
V+ is the activator for the npn transistor (Ic will from v+ to load (0) in npn.)
V- is the activator for pnp transistor (Ic will from load (0) to v- in npn.)
Thank you very much
Ab is the best of all to forget all the other shit completely
thanks a lot.
man your voice is like morgan freeman voice :) :D
thank u sir.
Thank u sir
Thnq🙏🙏
The efficiecy of class A is 20% less than that of class B 50% so B is better than A despite the distortion???
tnx
Class A B AB amplifier s video have from india
I am like number 888 😊😊😊
sir class AB amplifier's efficiency is 50 to 78.5%
If you say so!
what u mean by???
Yeah mate, easy enough to draw a ocl class a amplifier working in common collector configue.
You know how to make one thats class a and works in common emitter ? which is ocl? I bet you don't
not short enough
This helped a lot ! Thank you !