Input switching circuit for a television tuner immune to interference due to FM broadcasting signal

摘要

An input switching circuit for a television tuner includes first and second switching circuits provided between first and second input terminals to which a television signal and an FM broadcasting signal are input and an output terminal. The second switching circuit passes the FM broadcasting signal when receiving the FM broadcasting signal while blocking the FM broadcasting signal when receiving the television signal between the second input terminal and the output terminal. The second switching circuit includes first two diodes connected in series with each other between the second input terminal and the output terminal, which are turned off when receiving the television signal and turned on when receiving the FM broadcasting signal; and a second diode connected between the node between the first two diodes and the ground, which is turned on when receiving the television signal and turned off when receiving the FM broadcasting signal.