This study focuses on the design of microelectromechanical (MEMS) capacitive microphones before the read circuit, due to portable low voltage operation of the electronic products increasingly robust, therefore, will focus on mobile applications microelectromechanical (MEMS) condenser microphone in the low Voltage low power operation under the preamplifier. Micro-electromechanical condenser microphones contain two main circuits, one for the center-point self-bias capacitor-to- voltage converter circuit, and the other for the amplifier. Among them, the amplifier is related to the characteristics of the signal in this paper, the beginning of the design of the general second-order operational amplifier, although the amplifier can smoothly amplify the signal, at a fixed magnification, the different input swing, and frequency. Corresponding to the ideal magnification under the signal is different. Thus, the design of the second class op amp has a non-linear magnification and a lower output swing. So, then switch to symmetrical rail-to-rail operational amplifiers to improve the linearity and output swing of the circuit. The circuit of this study is based on Taiwan’s 0.35um (2P4M, 3.3V / 5V) process to complete the wafer production process. The output voltage range is approximately in the range of positive and negative voltage sources, and the total circuit power consumption is about 200uW. In addition to the design of low-pass filter and high-pass filter, thereby reducing the high-frequency noise and filter out the input DC bias.