| 摘要 |
PROBLEM TO BE SOLVED: To provide a gain control amplifier circuit suitable for a reception circuit or the like of a mobile communication equipment that can control gain, without using an AGC amplifier so as to make the circuit small and to reduce the cost. SOLUTION: This gain control amplifier circuit is provided with a power amplifier 6, a detection circuit 7 that is connected to an output of the amplifier 6 to output a detection voltage signal, in response to the output power, a comparator circuit 8 that receives a reference voltage signal and the detected voltage signal and provides an output of a control voltage signal, in response to a voltage difference between both the received signals, and a matching circuit 5 that is connected to the input of the power amplifier 6, receives the control voltage signal and matches the impedance with the input circuit and adjusts a gain of the power amplifier 6 by applying the control voltage signal to a varactor element to change the input reactance of the power amplifier 6. Thereby, the gain can be controlled without the use of an AGC amplifier, the circuit is made small and the cost is decreased. |
