Amplifier with 2 AA battery

Output swing: +-1V
Output current: >500mA

I was amazed my 5 inches shelf speaker can play pretty loud with just 2 AA battery.

This kind of out put stage seems to work pretty well with full swing of power supplier. I am thinking about to up scale it to larger power.

PS: It is able to work in Class B, with extremely low distortion.


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An interesting design. Would actually make a rather better headphone amp or discrete opamp replacement. As an opamp it can easily be scaled to any voltage by a simple change in R8 to set current for Q8-10 to keep things under soa. As for the class of operation I call it one of those cheating class A types since the lower output transistor never actually turns off. It goes down to idle current and lingers there till the next cycle. As a power amp it is only capable of about 1-2 watts because the available drive to the upper output transistor is limited by R9 and VBE of Q11 forming a current limiting effect on Q12 which is also responsible for Q11 never turning off.