| 摘要 |
PROBLEM TO BE SOLVED: To provide an interface circuit which is simple in configuration and of a low cost. SOLUTION: This circuit is a switched capacitor type interface circuit connected to a capacitive sensor with two capacitances C1 and C2 whose values vary. It is provided with an OP amplifier A1 between whose output and inverted input terminals a feedback and sampling capacitance C3 is connected and a hold capacitance C4 connected between the OP amplifier A1 and a reference voltage source. One terminal of each capacitance C1, C2 and C3 is connected to the inverted input terminal of the OP amplifier A1. The outer terminals of the capacitance C1 and C2 are connected to an electric supply and the capacitance C3 is short-circuited at clocksϕ1. The outer terminals of the capacitances C1 and C2 and the output terminal of the OP amplifier A1 are each connected to the non-inverted input terminal of the OP amplifier A1 at clocksϕ2.
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