A systematic methodology for opamp synthesis is presented. Based on this methodology, an automatic computer-aided design (CAD) tool called OTACAD is developed. OTACAD directly uses HSPICE as the si-mulator and a lookup table to model MOSFET in saturation region without complex equations. So it can design opamps in deep-sub-micron technologies and is suitable for various CMOS processes. Then, A sample opamp is designed by this tool in a 0.13-um CMOS process and used in the first stage of a 12-bit 200MS/s pipeline ADC. This ADC achieves a SNDR of 74.9dB, a SFDR of 93.0dB for a 84.2MHz input signal. In addition, several different CMOS processes have been tested to verify its adaptability.