CAPACITANCE CHANGE DETECTION CIRCUIT AND CONDENSER MICROPHONE DEVICE

摘要

PROBLEM TO BE SOLVED: To solve the problem that it takes time to charge a microcapacitor on start-up of a condenser microphone device using an MEMS (Micro Electro Mechanical Systems) microphone. SOLUTION: A lowpass filter (LPF) 26 comprising a high resistor R1 and a capacitance C1 is provided between one terminal of a condenser Cm constituting the MEMS microphone and a charge pump for charging Cm. The LPF 26 is provided with a diode D1 to be a forward bias when starting charging in parallel. A capacitance C2 and a high resistor R2 are connected in parallel to a feedback route that connects an inverted input terminal of an operational amplifier 28 connected to the other terminal of Cm and an output terminal, and a diode D2 is connected to C2 and R2 in parallel and in the direction of being a forward direction bias when starting charging. COPYRIGHT: (C)2008,JPO&INPIT