Research And Application Of CMOS Bandgap Reference

As a basic circuit of the integrated circuit, the reference is widely used. The accuracy and stability of the reference in the chip is better than the external power supply of the chip.The performance of the reference govern the the stability of the whole circuit.It’s crucial that bandgap reference has low temperature coefficient,low voltage,low power consumption and high power supply rejection ratio in analog/digital converters,digital/analog converter,dynamic memory,flash memory,etc.Bandgap reference with low temperature coefficient,low voltage,low power consumption and high power supply rejection ratio is the best performance reference circuit in variety of reference voltage source circuit.This paper introduces the specification and fundamental theory of bandgap reference and the basic circuit configuration.Hence, the work of this thesis is the design of a low voltage low power CMOS bandgap reference voltage source.The paper utilizes the current-mode structure to achieve the working under low power supply. The Vbe lineaization compensation method is used to carry out higher-order temperature compensation.In order to improve the PSRR( power supply reject ratio,PSRR) of bandgap reference, a voltage subtractor circuit is inserted into the conventional bandgap reference.The subtractor introduces the supply noise directly into the feedback loop of the bandgap circuit which could help to suppress supply noise.At the end of this paper also provides the application of CMOS bandgap voltage reference in LDO(Low Drop-Out Voltage Regulator,LDO)and in the current source.Based on SMIC 0.18μm CMOS process,the bandgap reference is simulated by Cadence spectre.Its output voltage is 700.1mVThe. temperature coefficient is 6.855ppm/℃ in the temperature range-40~125℃.PSRR at low frequency is-95 dB.The power supply stability is 0.2%in the the reference voltage range 0.6~1.8V.The phase margin of the bandgap reference is 61°.The low-frequency-loop gain is-85.When starting circuit is working,start time is 4μs.The temperature coefficient of the bandgap current source is 40ppm/℃ in the temperature range-40~125℃.The low dropout regulator is simulated by Cadence spectre.Its load regulation is 0.005% in the load current range 10~1000μA.Its power supply stability is 0.25% in the the reference voltage range0.6~1.8V.PSRR at low frequency is-65 dB.