Clamping circuit

DETAILED DESCRIPTION The present invention has been made in consideration of the above situation, and has as its object to provide a clamping circuit which can widen a setting range of a reference voltage as a clamping voltage and allows easy circuit design even when a power supply voltage is lowered.
The clamping circuit of the present invention comprises a signal input terminal to which an input signal voltage is supplied through a coupling capacitor, a reference voltage generating means, a voltage comparison means including an operational amplifier, having one input terminal to which the input signal voltage supplied to the signal input terminal is applied and the other terminal to which a reference voltage generated by the reference voltage generator is applied, for comparing the two input voltages, a bias voltage supplying means, and a switch means which is inserted between the bias voltage supplying means and the signal input terminal and is on ON/OFF-controlled based on the output from the voltage comparison means.
In the clamping circuit of the present invention, the input signal voltage is compared with the reference voltage by the voltage comparison means, and the switch means is ON/Off-controlled on the basis of the comparison result.
When the switch means is enabled, a bias voltage of the bias voltage supplying means is supplied to the signal input terminal, and the input signal voltage is clamped at a voltage equal to the reference voltage.
When the switch means comprises, e.
g.
, a CMOS transfer gate, a voltage drop does not occur across the switch means regardless of the bias voltage.