| 摘要 |
PURPOSE:To improve the attenuation effect, by constituting a bridge circuit with at least one varactor diode for a capacitance circuit and changing the capacitance value of the varactor diode corresponding to the change in an AGC power supply. CONSTITUTION:One capacitance circuit C1 connected to a signal input terminal (a) out of four capacitance circuits C1-C4 constituting the bridge circuit 1 is formed with the varactor diode, and the other circuits C2-C4 are fomred with a fixed capacitor. When an AGC power supply E is small, the potential difference applied across the diode C1 is small, the capacitance value is the largest, and as the AGC power supply is increased, the potential difference applied across the diode C1 is larger, the capacitance value is reduced, the circuit 1 approaches the equilibrium and the input signal is greatly attenuated. Thus, a large attenuation factor is obtained between the unbalance state and the equilibrium of the circuit 1. |
