For maximum gain, both input and output ports are conjugately matched

Due to the fact that , the output termination affects input termination
and vice versa.

Substitute (126) into (125), we have

Substitute (125) into (126), we have

By the solving (130) and (133), the optimum source termination, ,
and the optimum load termination, , are found to be

Under the condition that both the input and output termination are conjugated matched, all power
gains are equal and they have a value of

It can be shown that

so the maximum stable gain from an amplifier is

**Example** In a 50 system, a transistor has the following S-parameter at 1.3 GHz.
Find the optimum terminations for maximum power gain.

**Solution**
*K*= 1.032 > 1 , the transistor is unconditionally stable.