# Complementary common-emitter circuit

This complementary common-emitter circuit has special feature that can be applied in 2 model.
– Low distortion buffer
– The low power output circuit

How it works
In Figure 1 quiescent current flow through T1 and T2 as voltage (U) and R1, R2 sequence. Look at the circuit will see that difference normal circuit at both base lead is connected together. But usually will connected to the diode, which current that flow through diode will cause input resistances changes, result to quiescent current also changes.

In this circuit the quiescent current of T1 has value equal (U – 0.6) / R1 , and T2 = (U – 0.6)/R2
Assume the current gain of T1 and T2 high and same voltage across R3 will lower effect to the circuit. Normally R1 will use to equal R2 and relationship of the C2, C3 and C4 depend on the lowest frequency of the circuit.

If T1 and T2 have the current gain same together. And R1 = R2 will no DC voltage show at R3 cause not need to put C1. And if this circuit get signal from Op-amp then can remove both R3 and C1 away.

This circuit is designed as the class A buffer circuit. By Power loss in R4 is I^2*R4 ; I = (U-0.6)/ R
R4 is lower; R= R1 – R2