POWER AMPLIFIER BIAS CONTROL CIRCUIT AND METHOD

摘要

A control circuit for a multi-stage power amplifier (such as in a portable radio transmitter) compensates for fluctuations in ambient temperature, load, signal level and power supply voltage. The control voltage is set by comparing a biasing level which is related to the amplifier input signal level to a voltage proportional to the power supply current of the last stage of the amplifier. The control voltage resulting from the comparison establishes the operating point of the last stage of the power amplifier.