高精度电流偏置电路的设计

Design of a high precision reference current bias circuit

提出了一款应用于RF无线收发芯片的高精度电流偏置电路。综合考虑功耗、面积和失调电压对基准电压的影响,设计了一款符合实际应用的带隙基准电路。并以带隙基准电路作基准电流源的偏置,采用电压电流转换器结构设计了具有高电源电压抑制比(PSRR)的基准电流源。电流镜采用辅助运放的设计方法来提高电流镜的输出阻抗,减小沟道调制效应对输出的基准电流的影响,从而提高输出基准电流的精度。采用0.35μm CMOS工艺设计芯片版图,版图面积为0.18 mm2。提取寄生参数(PEX)仿真结果表明,该电路在-55℃^+90℃范围内的温度系数为15.5 ppm/℃,室温下基准电压为1.203 5 V;在低频段电流源的电源抑制比为90 dB;在外接电阻从1 kΩ~400 kΩ变化时,输出基准电流误差范围是0.000 1μA。

A high accuracy current bias circuit is presented in this paper, which can be used in RF wireless transceiver chip. This paper designs a practical application of the bandgap reference circuit, with consideration of the power, area and offset voltage. This paper adopts the bandgap reference circuit and a voltage to current converter structure to design a high power supply rejection ratio design （PSRR） of the reference current. Current mirror with auxiliary operational amplifier （gainboost） is to improve the output impedance, and to reduce the influence of modulation effect on the reference current, so as to improve the precision of output current reference.The reference current bias is simulated based on 0.35 μm technology standard CMOS process. The layout area is 0.18 mm2. Planning parameters extraction （PEX）simulation results show that the reference voltage is 1.203 5 V, temperature coefficient in the range of -55℃～＋90℃ is 15.5 ppm/℃, the power supply rejection ratio in low frequency is 90 dB, when the outside resistor is from 1kΩ～400kΩ, the output reference current error range is 0.000 1 μA.