Temperature,supply voltage and process variation independent CMOS current reference
Yan Xiao-lang · Journal of Zhejiang University(Engineering Science) · 2008
The bipolar transistors or the resistors in the traditional current reference were replaced by MOS transistors working in the subthreshold region to achieve an all CMOS current reference.The body effect of PMOS transistors was used to do further temperature compensation.The power supply reject ratio(PSRR) was improved by adopting the cascode and feedback structure.The proposed design exploited the relationship among the threshold voltage,the electron's(hole's) mobility and the MOS's source-drain current in the subthreshold regime to reduce the impact of process variation to the reference current.The circuit was designed and simulated by using CSMC's 0.5 μm mixed-signal process to provide a 1.62 μA reference current.Considering the temperature,supply voltage and process variation,the temperature drift coefficient was 1.58×10-4%/℃,the PSRR was 90.5 dB and the error caused by process variation was only ±3.5%.