A high power supply rejection ratio (PSRR) CMOS band-gap reference (BGR) with 1.2 V operation is proposed in this paper. The reference features include an error amplifier with a trimming circuit and a trimming resistor array on the chip. Local positive feedback is used in the error amplifier to obtain high gain. By trimming the resistor array, the PSRR of the error amplifier is trimmed around one to obtain a high PSRR. The trimming resistor array is controlled externally. The post simulation results indicate that the PSRR is up to ?130 dB@DC and ?89 dB@10 kHz. The experimental results show that, under a supply voltage of 1.2 V the measured PSRR is ?103 dB@dc and ?74 dB@10 kHz.