| 摘要 |
PROBLEM TO BE SOLVED: To alleviate an increase in a capacitance value of a feedback capacitance and alleviate deterioration in noise characteristics, when a signal band width is set to a low value for a channel selecting filter in a reception circuit. SOLUTION: The semiconductor integrated circuit includes the reception circuit for receiving an RF reception signal and the channel selecting filter. The channel selecting filter is composed of a cascade connection of a first stage filter and a second stage filter. The first stage filter is composed of a complete integrator including a first stage operational amplifier OPA2, a first input resistor R1, and a first feedback capacitance C. The second stage filter is composed of an imperfect integrator including a second stage operational amplifier OPA1, a second input resistor R1, and a parallel connection of a second feedback capacitance C and a variable feedback resistance R3. A ratio Q of a resistance value R3 to a resistance value R1 when a cut-off frequency is set low, is set smaller than that when the cut-off frequency is set high. COPYRIGHT: (C)2011,JPO&INPIT |
