Diagram Guide

This is 2X1W audio amplifier circuit with mini-KA2209 IC. It may work well from 3-12V DC and will work from a battery since the quiescent current drain is low. It requires no heat sink for normal use. Input and output are both ground referenced. Maximum output is obtained with a 12V power supply and 8 ohm speaker, however, is especially suitable for driving headphones from a supply as low as 3V.

Amp mini circuit only a few external components, the IC contains most of the necessary circuits. R1, R2 and R3, R4 are the resistances of feedback. C1 provides power supply decoupling. C2 and C3 are the input coupling capacitors, which block any DC that might be present on the inputs. C4, C5 DC block in the feedback loop of the inverting input and C6, C7 are the output coupling capacitors. C8, C9 and R5, R6 act as a Zobel network to provide a high frequency load for stability in the frequencies where the inductive reactance of the loudspeaker can be strong too. The boat provides the attenuation of input level.

C1,C2,C3 : 10 uF/25V ecap
C4,C5 : 100 uF/16V ecap
C6,C7 : 470 uF/16V ecap
C8,C9 : 100 nF poly
R1,R3 : 1k Resistor
R2,R4 : 100R Resistor
R5,R6 : 4R7ohm Resistor
Pot1 : 10k dual gang log pot
IC1 : KA2209 Integrated Circuit