| 摘要 |
PROBLEM TO BE SOLVED: To improve the noise figure by not causing reduction in the circuit impedance even when a resistance of a bias resistor is decreased to increase a forward current of a PIN diode in the AGC circuit employing the PIN diode. SOLUTION: PIN diodes D1-D3 with a characteristic whose high frequency resistance varies with a forward current are connected to the circuit so that they are forward-biased between an AGC signal level and a prescribed voltage level (e.g. earth level). A bias resistor R3 is inserted to any of the PIN diodes D1-D3. A high frequency signal is given to an input terminal 1. A coil L1 is inserted in series with the bias resistor R3 and a high frequency signal is outputted from a terminal 2. |
