Active filter type signal adjusting circuit

Abstract

A first operational amplifier differentially operates a signal to be adjusted input by an input unit and an adjusted signal output by an output unit. A second operational amplifier differentially operates a first output from the first operational amplifier and the adjusted signal. A buffer supplies a second output from the second operational amplifier to the output unit as the adjusted signal. A first adder obtains a sum component of a first signal obtained by multiplying a first variable m with the signal to be adjusted and a second signal obtained by multiplying a second variable 1-n with the adjusted signal. A first capacitor superposes the sum component of the first and second signals on the first output to supply a superposed signal to the second operational amplifier. A second adder obtains the signal to be adjusted or a component obtained by multiplying the first variable m with the signal to be adjusted as a third signal. A second capacitor superposes the third signal on the second output to supply a superposed signal to the buffer. The first and second variables m and 1-n are selected as desirable values in an adjusting mode and are respectively set to be m=n=1 (where 0.ltoreq.n and m.ltoreq.1) in a non-adjusting mode.