Class B push-pull amplifier (question)

Thread Starter

Shayan22h

Joined Oct 24, 2012
30
hey guys i have made a Class B push-pull amplifier where the current is supposed to be amplified but in fact there is no increment in the output current .
i have 2V input ac voltage so at the end i get 2V voltage between the two transistors obviously whatever load i place there the current will be 2v/RL,, so my question is we could get the same current with placing the RL in series with input ac voltage 2v so what is the point of this Class B push-pull amplifier ???
and i know as it is shown on the green graph the current going through the transistors have been amplified but this cant help the output current since the voltage difference between the two transistors is always equal with the input voltage !
cheers and thanks for ur time !
 

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Thread Starter

Shayan22h

Joined Oct 24, 2012
30
thanks for ur reply :) well i don't see anything wrong with Q2 it is a PNP transistor
i chose my transistors based on this page, the designer has recommended these 2 transistors :)
could u tell me what wrong is with Q2 plz ?
 

studiot

Joined Nov 9, 2007
4,998
It's a bit difficult to follow your circuit, the way you have drawn it, but one of your transistors is the wrong way round. If you look D1, D2 and the base -emitter diode of Q1 clamp the collector-base voltage of Q2 to three diode drops max.
 

Thread Starter

Shayan22h

Joined Oct 24, 2012
30
A tip
Q2 emitter should be connected to the output not to Vee.
woow thank u so much what a stupid mistake i made :)))

ok now one more question please, as it is shown on the oscilloscope i measured the current on the base of the NPN transistor and it is not fluctuating now and it is constant 1mA, why is it the case ? the current is fluctuating all over the circuits and it makes sens for me to also fluctuate in the base of the transistors and it was also fluctuating before u would give me hint to correct Q2
 
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