Patent ID: 8229384
Filing Date: 2012-07-24
Classification: H03H

Abstract:
1. A filter circuit comprising: a first input terminal for accepting a first input signal; a first filter process unit which executes a filter process of the first input signal inputted through the first input terminal; a first output terminal capable of outputting a processed result in the first filter process unit; a second input terminal for accepting a second input signal which is in a relation of a complementary level to the first input signal; a second filter process unit which executes a filter process of the second input signal inputted through the second input terminal; and a second output terminal capable of outputting a processed result in the second filter process unit, wherein the first filter process unit and the second filter process unit include a plurality of first capacitors for forming a high-pass filter; a plurality of second capacitors capable of altering a cutoff frequency of the high-pass filter by being connected in parallel with the first capacitors; a first switch capable of coupling one terminal of one of the second capacitors to one terminal of one of the first capacitors; a second switch capable of coupling the other terminal of said one of the second capacitors to the other terminal of said one of the first capacitors; a resistance for attenuating an amplitude of an input voltage to be fed to said one of the second capacitors, by being connected in series with said one of the second capacitors; a third switch capable of coupling the resistance to one end of said one of the second capacitors; and a fourth switch capable of feeding a predetermined bias voltage to the other end of said one of the second capacitors, wherein the second capacitor is charged through the resistance in a state where the first switch and the second switch are turned OFF and where the third switch and the fourth switch are turned ON, and wherein the first input terminal and the second input terminal are coupled through the resistance.