This paper describes a high signal-to-noise ratio capacitive sensing transducer with high power efficiency and high area efficiency. The circuit is an example of capacitive circuit and is based on a capacitive feedback charge amplifier. 78.6dB SNR in audio band is achieved with less than 0.5 /spl mu/W power consumption by making use of a floating-gate transistor. This design gives us the flexibility of controlling the charge on the floating node. The microphone sensor is interfaced with the amplifier to measure the performance of the transducer.