DATA ACQUISITION CIRCUIT

PROBLEM TO BE SOLVED: To provide the sampled value of a small through rate to an AD converter with no use of an analog switch, a fast sampling pulse holding capacitor nor a buffer amplifier. SOLUTION: This circuit includes a differentiation circuit 11 which differentiates an input signal 1, a strobe circuit 12 which generates a sine wave 3 and a cosine wave 5, a pair of multiplication circuits 20 and 60, a variable gain amplifier 14 and a differential amplifier 15. Then the circuit can provide the sampled value having its through rate substantially equal to zero when an AD converter 18 performs the AD conversion since the signal of a terminal 8 is equal to a signal having its through rate of zero that is coincident with the value of the signal 1 in an AD sampling mode of AD conversion. The circuits 20 and 60 are Gilbert type multiplication circuits and can be easily turned into an IC including the converter 18.