一种用于低边电流检测的可编程增益放大器

A programmable gain amplifier for low-side current sensing

基于0.5μm BCD工艺,设计了一种用于低边电流检测的可编程增益放大器(Programmable Gain Amplifier,PGA)。采用了电流模闭环可编程增益放大器结构,将传统电压模反馈电阻网络对采样电路的漏电流影响减小到纳安级别。设计了一种全差分高精度可变跨导放大器,给PGA提供了更加精准的可变增益。仿真结果表明,PGA放大倍数为4时,测量误差为0.2%,PGA放大倍数为256时,测量误差为3.11%,总谐波失真小于0.021%,芯片面积为1.5 mm×1.5 mm。

A Programmable Gain Amplifier(PGA) for low side current sensing is designed in 0.5 μm BCD process. A current-mode closed-loop programmable gain amplifier is used to reduce the influence of the traditional voltage-mode feedback resistor network on the leakage current of the sampling circuit to the level of nA. A fully differential high precision transconductance amplifier is designed,gives the PGA a more accurate and variable gain. The simulation results show that PGA measuring error is 0.2%in gain 4 and 3.11% in gain 256. Total harmonic distortion is less than 0.021%,and the circuit area is 1.5 mm×1.5 mm.