a communication apparatus is small in power consumption and suitable for use in a portable radio communication apparatus . the communication apparatus includes a semiconductor power amplifier integrated circuit which uses a gaas junction type fet having a gate bias terminal to which a gate bias voltage is applied . the integrated circuit decreases its amount of power consumption in a manner that the integrated circuit is operated to perform an amplification operation during a communication operation and not operated when a communication is interrupted or a time slot is not allotted to the communication apparatus itself . a detector detects a portion of a high - frequency signal to the amplifier circuit to provide an input to a gate bias generator which provides an input to an adder circuit , the output of which controls the bias on the power amplifier .