AM/FM RADIO RECEIVER AND RECEIVING SEMICONDUCTOR INTEGRATED CIRCUIT USED FOR SAME

摘要

The first-stage amplifier of an AM receiver circuit and the first-stage amplifier of an FM receiver circuit are contained in an IC (2) as differential amplifier circuits (3, 4). The AM differential amplifier circuit (3) is connected to a first pad (P1) connected to the duplex antenna for AM/FM. An FM separation capacitor (C1) and the FM differential amplifier circuit (4) are connected parallel to the AM differential amplifier circuit (3). Consequently, a pad capacitor (Cp) is formed between the first pad (P1) and the board, and allowed to function as a capacitor for absorbing only the signal in the FM frequency band and passing the signalin the AM frequency band. Therefore, the AM separation coil which has been conventionally an external component is made unnecessary.