Patent ID: 6791401
Filing Date: 2004-09-14
Classification: H03H

Abstract:
A continuous-time analog filter comprising:a first filter for amplifying with a prescribed amplification gain signal having a frequency within a certain band in an input signal, and passing the amplified signal; and a gain control circuit configured for controlling the amplification gain in said first filter, wherein said gain control circuit includes: a second filter for amplifying said input signal with said predetermined amplification gain, and rejecting interference waves contained in said input signal, detecting circuits configured for detecting maximum values of amplitudes of output signals of said first and second filters, and a determining circuit configured for receiving results of detection of said detecting circuits, and controlling the amplification gain of said first filter based on a comparison between the output signals of said first and second filters, wherein said first filter has an operational transconductance amplifier, and said gain control circuit controls a conductance value of said operational transconductance amplifier employed in said first filter.