US 4,301,420 A · Frequency characteristic-adjusting apparatus

Abstract

A frequency characteristic-adjusting apparatus comprising a filter circuit formed of a first variable gain amplifier and a capacitor, a second variable gain amplifier for amplifying an output signal from the filter circuit, an amplifier for amplifying a signal denoting a difference between the amplitudes of an input signal to the filter circuit and an output signal therefrom, and an adder circuit for adding together output signals from the second variable gain amplifier and difference signal amplifier, and wherein the first and second gain amplifiers are connected to potentiometers, and the gains of the first and second variable gain amplifiers are varied in accordance with changes in the voltage supplied from the potentiometers to the amplifiers, while maintaining the prescribed relationship between the gains of the first and second variable gain amplifiers.

Claims10

Dependent claims

A frequency characteristic-adjusting apparatus comprising:

gain control signal means,
a filter circuit having capacitive means and variable impedance means, the impedance of said variable impedance means being varied in accordance with an output control signal from said control signal generating means to adjust a cut-off frequency of said filter circuit;
first amplifier means for amplifying a signal corresponding to an output signal from said filter circuit;
second amplifier means for amplifying a signal corresponding to a difference between an input signal to said filter circuit and an output signal therefrom;
and
adder means for adding together output signals from said first and second amplifier means, wherein at least one of said first and second amplifier means is connected to said gain control signal means and is formed of a variable gain amplifier circuit whose gain is controlled in accordance with change in an output control signal from said gain control signal means.

3 more elements

A frequency characteristic-adjusting apparatus comprising:

gain control signal means;
a plurality of cascade-connected filter circuits at least one of which includes capacitive means and variable impedance means, the impedance of said variable impedance means being varied in accordance with an output control signal from said control signal generating means to adjust the cut-off frequency of a corresponding one of said filter circuits;
first amplifier means for amplifying a signal corresponding to an output signal from the last one of said filter circuits;
a plurality of second amplifier means for amplifying signals each corresponding to a difference between the input signal and output signal of a corresponding one of said filter circuits;
and
adder means for adding together output signals from said first and second amplifier means, wherein at least one of said first and second amplifier means is connected to said gain control signal means and is formed of a variable gain amplifier circuit whose gain is controlled in accordance with change in an output control signal from said gain control signal means.

3 more elements

Dependencies are inferred from the claim text.

Frequency characteristic-adjusting apparatus

Life of this patent

Frequency characteristic-adjusting apparatus

Life of this patent

Abstract

Claims10