针对生物信号微弱、变化范围大等特点设计了一种用于检测微弱电流的全差分跨阻放大器(TIA)电路结构。不同于传统电路的单端输入, 该结构采用高增益的全差分两级放大器实现小信号输入及轨到轨输出。基于CSMC 0.18μm CMOS工艺, 采用1.8V电源电压对设计的电路进行了仿真, 仿真结果表明：TIA输入电流动态范围为100nA~10μA, 最大跨阻增益达到104.38dBΩ, -3dB带宽为4MHz, 等效输入噪声电流为1.26pA/Hz。对电路进行跨阻动态特性仿真表明, 在输入电流为100nA时, 输出电压的动态摆幅达到3.24mV, 功耗仅为250μW, 总谐波失真(THD)为-49.93dB。所设计的高增益、低功耗、宽输入动态范围TIA适用于生物医疗中极微小生物信号的采集, 可作为模块电路集成在便携设备中。

Biological signals are weak in large variation range, thus a circuit structure of fully differential trans-impedance amplifier (TIA) was designed to detect weak current. Different to traditional single-ended input structre, a high gain and fully differential two-stage amplifier was applied to realize small signal input and rail-to-rail output. Simulations were performed with 1.8V supply voltage based on CSMC 0.18μm CMOS process. Simulation results show that the TIA achieves an input current dynamic range of 100nA~10μA, a maximum transimpedance gain of 104.38dBΩ, -3dB bandwidth of 4MHz, and equivalent input noise current of 1.26pA/Hz. Simulations on transimpedance dynamic characteristics indicate that, when the input current is 100nA, the output voltage swing is 3.24mV, the power dissipation is only 250μW, and the total harmonic distortion (THD) is -49.93dB. The designed high gain and low power consumption TIA can be applied to collect very weak biological signals, and integrated as a module circuit in portable equipments.