Filter Adjustment Circuit

摘要

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 circuit 1 is inputted to a Gm-C filter 2 to be filtered and then converted by a conversion circuit 3 to a digital signal. A reference signal RS from the reference signal generation circuit 1 is converted by a conversion circuit 4 to a digital signal. The two converted signals are held in time series in a holding circuit 5. A timing generation circuit 6 generates an update timing signal en based on a reference time-series signal ref from the holding circuit 5. A control signal generation circuit 7 generates 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 5. The control signal CS is inputted to the Gm-C filter 2 in response to the update timing signal en to adjust the gain of the Gm-C filter 2. As a result, variations in the response characteristics of the Gm-C filter 2 are adjusted with high accuracy with a simple circuit structure.