Abstract: A voltage-based CMOS bandgap reference circuit is proposed for the application requirements of implantable neurostimulators in biomedical chips. The cascode current source and the two-stage op-amp structure are used to improve the power supply rejection ratio and the voltage line regulation. Based on the traditional widlar current source structure, the two-stage op-amp output feedback is introduced to provide a stable bias current for the op-amp itself, the bandgap core circuit and the temperature front-end. In order to eliminate the effect of the op-amp offset voltage Vos, a resistor trim matrix is designed according to the maximum range of resistance change of the process library, which improves the temperature coefficient of the reference voltage. The design circuit is based on TSMC 0.18 um BCD process, and the test results show that the voltage line regulation is 0.023% at 1.8 V-6 V, the power supply rejection ratio is −78 dB at 10 Hz and −55 dB at 100 Hz, the temperature coefficient is 16.68 ppm at −40℃-125℃, the total power consumption of the circuit is 90 uW at 5 V, and the core circuit chip area is 0.15×0.38 mm².