Filter mit automatischer Grenzfrequenzregelung.

摘要

An cut-off frequency automatic adjusting filter includes a plurality of filters (2,10), one of them being a reference filter (2), and a feedback circuit for the reference filter. The feedback circuit is formed by a substracter (4), a full-wave rectifier (5), an integrator (6) and an error amplifier (7). A sqaure wave signal is inputted to the reference filter as a reference signal instead of a sine wave signal in the conventional filter. The feedback circuit generates an electrical signal which causes the cut-off frequency of the reference filter (2) and other filters (10) to be constant.