Patent ID: 7773271

Claim:
A filter circuit comprising: a first current mirror circuit that comprises a plurality of transistors and that passes a first mirror current according to a constant current; a second current mirror circuit that comprises a plurality of transistors and that, operating in inverted synchronism with the first current mirror circuit, passes a second mirror current according to a constant current; an input terminal via which an input pulse signal is fed in; a first transistor that, in response to the signal fed in via the input terminal and by using a supply voltage, makes the first current mirror circuit operate; a second transistor that, in response to the signal fed in via the input terminal and by using a ground voltage, makes the second current mirror circuit operate, the second transistor operating in inverted synchronism with the first transistor; a capacitor that is charged by the first mirror current and that is discharged by the second mirror current; and an output terminal via which a voltage at one end of the capacitor is fed out.