| 摘要 |
PURPOSE:To obtain an AGC circuit which has excellent temperature characteristics, includes an amplitude demodulating circuit, and is IC-implemented easily, by utilizing the amplitude demodulating circuit of a current balanced product type, a constant voltage source, and a DC differential amplifier. CONSTITUTION:An intermediate frequency signal applied to an input terminal 1 is applied to a current balanced product type amplitude demodulator 3 through an amplitude limiter 2 which eliminates an amplitude-modulated component. A detected output signal appearing at a load resistance R01 connected to a constant voltage power source 8 at the other end is led through a low-pass filter 7 to an output terminal 9, and also applied through a resistance R03 to a differential DC amplifier 6 together with an offset voltage obtained by dividing the voltage of the constant voltage power source 8. This offset voltage determines the input level of the start of AGC operation. On the other hand, an intermediate frequency signal applied to a carrier level controller 5 is brought under the level control of a control signal generated by the differential DC amplifier 6, and the resulting signal is applied to the amplitude demodulator 3 through a buffer amplifier 4. |
