PURPOSE: To reduce the power consumption and to suppress the nonlinear distortion by controlling the bias voltage of a class 'AB' amplifier in accordance with an output or input level.
CONSTITUTION: A detector consisting of a transistor TR Q0 for class 'AB' operation, a bias control circuit 1, a detector 2, a directional coupler 3, etc., is provided, and a part of the output signal is taken out by the directional coupler 3 and is detected by the detector 2 and is converted to a DC voltage. This detection voltage is inputted to the bias control circuit 1, and a control voltage V obtained by converting a supply voltage VCC, to a prescribed value is applied to a bias resistance circuit consisting of bias resistors R1 and R2. The bias voltage of the TR Q1 is changed in accordance with the level of the output signal power in this manner to correct the operation characteristic of the TR Q0. Consequently, the efficiency is improved as the whole in the allowable range of the output signal power, and the high frequency linear amplifier is made small-sized and low-power consumption.
SERA YASUO
SUDO MASAKI
OKUBO YOICHI
| JP57062418B | ||||
| JPS58124308A | 1983-07-23 |