Variable output amplifier

In a variable output amplifier apparatus, an input signal (SIN) is distributed by a distributing unit (1) as first signals (S1, S2, ..., Sn) to a plurality of variable gain units (2-1, 2-2, ..., 2-n) having different gains. Second signals (S1', S2', ..., Sn') generated from the variable gain units are combined by a combining unit (3) to generate an output signal (SOUT). A plurality of power supply control units (4-1, 4-2, ..., 4-n) apply power supplies (VCC1, VCC2, ..., VCCn) to the variable gain units, respectively. The variable gain units and the power supply control units are controlled by a control unit. When one of the variable gain units and one of the power supply control units are activated, the corresponding power supply is turned ON. When they are deactivated, the corresponding power supply is turned OFF.