Patent attributes
Operational amplifier circuitry drives a device which may be run with a combination of output signals fewer in number than the output signals delivered from plural output circuits. Each output circuit adjusts the gain of an input signal supplied to its operational amplifier. An output selector selects and outputs output signals from the output circuits necessary for driving the device. A decision circuit compares an output signal not selected with a reference signal to adjust the gain of the output circuits to thereby cancel the offset of the operational amplifier. The operational amplifier has sets of feedback elements different in number between the sets formed by capacitances. Switching is made from one set to another until the decision circuit makes an acceptable decision. Offset may thus be canceled during the operational amplification even in case capacitive or resistance element is connected in circuit outside the operational amplifier.
