POWER GAIN CONTROL SYSTEM

PURPOSE:To simplify the constitution of a power gain control system and to attain low cost by making the gain of plural stages of power amplifiers connected in series different from each other. CONSTITUTION:An H or an L signal is fed respectively to power amplifiers 2a- 4a selectively from bias voltage control circuits 6-8 by using digital control signal 10-12. When the H signal is impressed to the amplifiers 2a-4a from the bias voltage control circuits 6-8, the amplifier gain is set respectively to a gain such as 5dB, 5dB and 0dB and when the L signal is impressed, the gain is set to a gain such as 10dB, 15dB and 15dB, and the entire gain of a multi-stage amplifier is controlled depending on the state of the control signals 10-12. Since no D/A converter is employed, the system is realized by a low cost.