lecture31 Class B, Class AB and Class A Power Amplifiers

[@takbiatulislam8403]

Excellent! Crystal clear lectures. He explained a complex topic, power amplifier in a such a easy fashion, which requires an art. I would be happy to be his student. The style of delivering the lecture is so interesting as if he is telling his students a story. My best regards to him.

[@maresfillies6041]

I'd rather have Professor Roy as my EE prof then the one I have currently. :/ This guy is awesome and he doesn't read from powerpoint slides. :D

[@ymmen041294]

@ 20:22, in the circuit the input voltage is attached to base of Q2, however shouldn't it be connected to base of Q1 as well. Or else there will be dead band while negative half cycle of the input voltage.

[@SmithKerona]

No there won't be any dead band on the negative cycle since Q2 base is always 0.7V below its emitter (because of the presence of Q4). When the input voltage goes just below zero Q1 base is at 1.4V and the output voltage is at 0.7V. Hence Q1 is still conducting (the input voltage has to go to -1.4V for Q1 to stop completely conducting). When the signal reaches -0.7V the output voltage is at 0V and both Q1 and Q2 are conducting quiescent current. But the moment the signal goes below -0.7V, Q2 takes over right away because its emitter is at zero volts and avoid a cross over distortion.

[@GALA30live]

I dont find lecture 30 ? please post the link to it !

[@absound5818]

Kon se class ka amplifier best hota he

[@ArshadHaroon]

Hi Satish, your lectures are detailed and of course provide lots of information. I am an audiophile and would like to know in simple English. When I go to an electronic store to look for a high current home music amplifier in different brands, they tell me it is A, B, C and D class. I have two questions here please. What class is the high current amplifier and how do we know that it is a high current amplifier, does the specifications at the back of amplifier shows like in Mv like in milli amps or distortion or what. The high current amplifiers that are famous here in Canada are mostly Marantz amplifier and they are high end and expensive too. I hope you will describe to me so that I learn. I thank you in advance.

[@viswesh713]

hi arshad, class A amplifiers for best sound reproduction the whole signal will be amplified by one transistor and obviously no cross-over distortion but little THD and efficiency is less than 30% you have to burn watts to get few watts. class B amplifiers distorts but 50% efficient good at low volumes and bad at high volumes THD is high and cross-over distortion too class AB amplifiers are better than class B, class AB will have Vbe multiplier also called biasing circuit for output transistors, Vbe also works as thermal sensor, at few instants both PNP and NPN comes in conduction that leads to thermal runaway of transistors, if no proper bias circuit it distorts and if good bias less THD, less noise and efficient too. the famous output drivers are 2sc5200 and 2sa1943 class C good efficieny say 90% and lot of distortion too, not good for music class D nice amp, efficiency more than 90% and little THD, nice info here www.irf.com/application-family/_/N~1njcjq#tab-tab3 i used to design, build and repair them. thank you.

[@ArshadHaroon]

visweswara rao kalla Thanks so much visweswara, one another thing, when we talk about high current amplifiers or receivers, so do we call high current amplifiers as D class. Marantz receivers and amplifiers are expensive as compared to other receivers and are high current mostly. what do you say about it.

[@viswesh713]

Arshad Haroon i heard good about marantz (audiophile quality) you mentioned high current, based on topology(A,B,AB,C etc ). class A needs lot of power. goto diyaudio lot of info on it

[@ArshadHaroon]

Thanks, I got some idea.

[@ArshadHaroon]

visweswara rao kalla Here is one favor if you can please let me know based upon your knowledge. I want to know about this integrated amplifier model Sony TA-A400 100w/ch. Some of the specs indicate "2 channel integrated 100 w/ch @ 8 ohms Freq response 7Hz - 100kHz 0.05% THD 4 ohm to 16 ohm speaker load DC offset currently measures -3.8mV left, -1.2mV right (excellent)" My question is" is it high current amplifier?" and if not what do you think of the power and freq. response etc. I will appreciate your information. Thanks in advance.

[@jenishmange8994]

where is his first lecture

[@AntonBilbaeno]

No but he can build you the power supply and everything else for you to cook it yourself.

[@ibsenvalath]

lec 30 : watch?v=jdcnWoL02k4&list=PL2D75EC7EC87B37E0

[@jenishmange8994]

pls lemme know

[@SP330Y]

Great information so thank you for that but it is really annoying that somebody is always coughing throughout your presentation which makes it impossible to fully understand. The person that is coughing all the time should be ejected from the lecture so people who want to learn can learn.

[@437-m3j]

+SP330Y Get over yourself.

[@SP330Y]

thanks for your advice :)

[@deepaknagar4331]

Go back in time zone and ask him to go out of the class. He is really very irritating.

[@tpawlowskis]

can you cook me some indian rice