Patent ID: 7626524

Claim:
A multi-channel sample and hold circuit comprising: an operational amplifier having a pair of input terminals and a signal output terminal, one of the pair of input terminals being connected to a reference voltage; a plurality of electric charge setting channels each of which includes a signal input terminal, an electric charge setting capacitor, a first electric charge setting switch connected between the signal input terminal and one side of the electric charge setting capacitor, a second electric charge setting switch connected between the other side of the electric charge setting capacitor and the reference voltage, a channel separating switch connected between the other side of the electric charge setting capacitor and the other input terminal of the operational amplifier, and a holding switch connected between the one side of the electric charge setting capacitor and the signal output terminal of the operational amplifier; and a control circuit for selecting one of the electric charge setting channels to hold a signal that is inputted to the input terminal thereof, wherein: the control circuit turns off the first and second electric charge setting switches of the selected channel and turns on the holding switch and the channel separating switch of the selected channel to connect the electric charge setting capacitor of the selected channel between the other of the pair of input terminals and the signal output terminal of the operational amplifier; and the control circuit simultaneously turns off the other channel separating switches and the other holding switches of channels that are not selected by the control circuit to separate the other electric charge setting capacitors from the operational amplifier and turns on the other first and second electric charge setting switches to connect the other electric charge setting capacitors with the other input terminals of the channels that are not selected by the control circuit.