SAMPLE-AND-HOLD CIRCUIT

PURPOSE:To use stably the circuit even at a low voltage by driving a differential switch with a current mirror circuit. CONSTITUTION:A differential switch comprising transistors (TRs) Q6, Q7 is driven by the current mirror circuit consisting of TRs Q14, Q15. A current supplied from a TRQ11 flows to the TRQ14 and a resistor R13 by the operation of a comparator 6 during the sample period. A TRQ7 is turned on, a TRQ6 is turned off, a current I1 in response to the resistance ratio of the resistors R13, R6 flows to the TRQ7, the charge/discharge current required for the sample period and a current flowing to the TRQ6 at hold period are set freely by selecting optionally the ratio of the resistors R6 and R13 and the ratio of the resistors R6 and R14, thereby eliminating the saturation of the TRs Q2, Q6 and the limitation of the amplifier gain setting resistor R1. A bias voltage source for differential switch drive is not required.