| 摘要 |
PURPOSE:To obtain an AGC circuit which ensures a stable output amplitude with no effect of a temperature change by extracting not only signals but a reference potential out of an output stage of a main amplifier circuit. CONSTITUTION:A detection circuit 2 detects the output peak value of an amplifier circuit 31 which amplifies an input signal with the gain varying by a control signal. While only the DC component is extracted at a division point of a load resistance 32 of the circuit 31 through an LPF5. Then the output of the circuit 2 is compared with that of the LPF5, and a comparator delivers a control signal in response to the obtained difference of outputs. In such a constitution, the output signal of an AGC circuit is deflected in an amplitude of alphaRL.ILO centering on an output terminal potential VLO obtained in a no-signal mode. Thus the amplitude of a signal can be prescribed by a product of the resistance 32 and a current flowing to the resistance 32. Therefore the variation can be reduced effectively to the variance of the power supply voltage, temperatures, etc.
|
