一种应用于高精度ADC的可编程增益放大器的设计

Design of a Programmable Gain Amplifier for High Precision ADC

设计了一种应用于高精度ADC的可编程增益放大器(PGA)。整体环路采用可调节的反馈电阻来调节增益,同时适配可调节的反馈电容来稳定环路工作带宽。内部核心运放采用折叠共源共栅级加轨对轨共源级的两级全差分结构,其输入管采用PMOS管来降低噪声,同时使用输入尾电流监控和增益提高技术来提高环路的精度。仿真结果表明,该PGA对3种不同输入幅度的信号处理后,3 dB带宽稳定在13 kHz附近,信噪比均在100 dB以上,符合高精度ADC对前端信号处理的需求。

A programmable gain amplifier(PGA)for high precision ADC is designed.The overall loop adopts an adjustable feedback resistor to adjust the gain,and adopts an adjustable feedback capacitor to stabilize the loop operating bandwidth.The internal core amplifier adopts a two-stage fully differential structure of folded common source common grid stage and rail to rail common source stage,and uses PMOS tube for input transistor to reduce noise,while the input tail current monitoring and gain-boosting technique are used to improve the accuracy of the loop.The simulation results show that after processing signals with three different input amplitudes,the PGA has a stable 3 dB bandwidth around 13 kHz,and the signal-to-noise ratio is above 100 dB,which meets the requirements of high precision ADC for front-end signal processing.