The Analysis And Design Of CMOS Band-GAP Reference Based On Sub-Driven Op AMP

With the development of integrated circuit technology, it is very popular to use on-chip bandgap voltage reference in switching power supply. Reference is a power supply which can provide high precision and high stable base voltage. The performance of the reference is closely related to the performance of the switching power supply system, which makes it necessary to make sure the PSRR(Power Supply Rejection Ratio) of the bandgap reference is high enough.If the capacity of the bandgap reference on the power supply noise rejection is insufficient, this noise will be coupled to the output voltage of the power supply system through the reference voltage. Besides the PSRR, the temperature stability of the output voltage is also an important performance index. In addition, many applications require the circuit to be compatible with the standard CMOS process. Based on the above ideas,an improved bandgap reference based on the sub-drive operational amplifier is proposed. The self-biased sub-driven cascode amplifier insures a wider range of common input voltage than traditional ones;the negative feedback cascode output stage improves the PSRR of the whole circuit;the innovative bias circuit reduces the impact of the supply voltage on the bandgap reference;current squared circuit is used for second-order compensation, which can both effectively reduce the temperature coefficient of the bandgap reference and be realized in standard CMOS technology.The bandgap reference is simulated in TSMC 0.25um CMOS process and the HSPICE simulation results show that the bandpap voltage reference can work nomally when the supply voltlage is in the range of 1.8～5V;in the condition of 2V power supply voltage and room temperature, the low-frequency power supply rejection ratio is -91dB, the static power of the whole circuit is 1.674mW;in Room temperature, when the supply voltage changes from 1.8V to 5V, the power supply voltage regulation is 0.406mV/ V;when the temperature ranges from -40℃to 125℃, the temperature coefficient of the bandgap reference output is 6.67ppm/℃with a supply voltage of 2V;the output voltage is 1.267V The results show that the circuit has good performance and meets the design requirements.As the feature size of integrated circuit technology continues to reduce, analog circuit voltage is also decreasing steadily, which make it necessary to design low-voltage bandgap reference circuits. To soulve this problem,a CMOS bandgap reference with a sub-1V power supply voltage is proposed. The sub-driven operational amplifier is used to insure the power supply voltage to be less than 1V; the piecewise linear compensation circuit is used to reduce the temperature coefficient.This bandgap reference is simulated in TSMC 0.25um CMOS process and the HSPICE simulation results show that the bandpap voltage reference can work nomally when the supply voltlage changes from 0.8V to 1.8V;in the condition of 0.9V power supply voltage and room temperature, the low-frequency power supply rejection ratio is-45dB, the static power of the whole circuit is 61.52uW;in Room temperature, when the supply voltage changes from 0.8V to 1.8V, the supply voltage regulation is 3.71mV/V; when the temperature ranges from -15℃to 135℃, the temperature coefficient of the bandgap reference output voltage is 11.11ppm/℃with a supply voltage of 0.9V;the output voltage is 0.69V. The results show that the circuit has good performance and meets the design requirements.