Filter adjustment circuit

Abstract

In a filter adjustment circuit for an analog filter circuit such as a Gm-C filter, an input signal IS from a reference signal generation circuitis inputted to a Gm-C filterto be filtered and then converted by a conversion circuitto a digital signal. A reference signal RS from the reference signal generation circuitis converted by a conversion circuitto a digital signal. The two converted signals are held in time series in a holding circuit. A timing generation circuitgenerates an update timing signal en based on a reference time-series signal ref from the holding circuitA control signal generation circuitgenerates a control signal CS based on the reference time-series signal ref and a filter output time-series signal tgt, each from the holding circuit. The control signal CS is inputted to the Gm-C filterin response to the update timing signal en to adjust the gain of the Gm-C filter. As a result, variations in the response characteristics of the Gm-C filterare adjusted with high accuracy with a simple circuit structure.