An amplifier includes a differential amplifier stage, a voltage amplification stage and a power output stage. The bias level of the output stage is proportional to current through the voltage amplification stage. The voltage amplification stage includes a current mirror whereby controlled current through a first leg of the current mirror controls current through the remaining, second leg, which, in turn, determines the bias level of the power output stage. Control circuitry senses a parameter of the amplifier, such as DC bias or input signal level to generate a control signal which is applied to the first leg of the current mirror to thereby control bias level of the power output stage.
