| 摘要 |
PURPOSE:To make unnecessary the transformer and to enable the circuit to be incorporated on the same semiconductor substrate, by providing the carrier level variable circuit controlled with the level automatic control signal with the input terminal of carrier signal. CONSTITUTION:The multiplier type modulation circuit 6 is formed with the balanced modulation circuit 4 and the modulated signal input circuit 5. Further, the carrier level variable circuit having the carrier input terminals 3, 3' is formed with the resistor R10 and MOSFET.Q7 for the attenuator, and the attenuation control voltage Vc being the AGC signal is fed to the gate of Q7. The signal voltage ep and the carrier voltage ec are input to the modulation circuit 11 thus constituted, and the output is fed to the low pass filter 12. The output of the filter 12 is separated with the hybrid transformer 13. One output separated is fed to the band-pass filter 14 and monitor signal only is picked up. The picked-up signal is amplified, rectified and extended to be the gain control signal 23. |
