Automatic gain control circuit using PIN diode capable of improving noise figure while improving frequency band characteristic and bidirectional CATV receiver including such circuit

摘要

An input high frequency signal passes through a PIN diode having a variable high frequency resistance and is output from an AGC circuit. The PIN diode is connected so as to be biased forward between an AGC signal level and a fixed voltage level (such as ground potential). A bias resistor and a coil are connected in series between a node on the output side of the PIN diode and a node supplied with the ground potential. More specifically, the resistor and the coil are inserted in parallel between the transmission path for high frequency signals and the ground potential.