Research And Design Of A Programmable Gain Instrumentation Amplifier

A programmable gain instrument amplifier is a versatile electronic instrument that uses analog circuitry and digital signal processing technology for amplification,filtering,and digitization of external electrical signals.It is widely used in fields such as industrial control,instrument measurement,biomedical research,and sensor signal detection due to its programmability,high accuracy,and low noise features.This article provides an in-depth analysis of the main design concepts of current instrument amplifiers,compares and contrasts the six widely used design structures,and ultimately selects a three operational amplifier architecture as the final design scheme.The focus of the design is on the individual operational amplifier in the instrument amplifier system.The designed single amplifier utilizes tail current self-biasing to improve slew rate,current mirror coupling to achieve differential-to-single-ended conversion,and AB-class output and protection loop in the output stage.To meet the different gain and bandwidth requirements of instrument amplifiers for different application scenarios,a load-programmable feedback network was designed to control the gain and bandwidth of the instrument amplifier through inputting a digital signal,thereby improving data processing efficiency and accuracy.This article employs the 0.25μm BCD process and Cadence software to simulate and analyze the parameters of this design.The designed instrument amplifier demonstrates an overall gain adjustment relative error of less than 0.03% under full temperature,an offset voltage not exceeding 50 u V at room temperature,an input bias current of less than 30 n A,an input and output range that swings from-VS+1.5V to VS-1.5V,a common mode suppression ratio that exceeds 100 d B at room temperature and 80 d B at full temperature,a power supply suppression ratio of not less than 75 d B,a-3d B bandwidth higher than10 MHz at room temperature for G=1,G=2,higher than 8MHz for G=4,and higher than2.5MHz for G=8,a slew rate not less than 20V/us,a settling time not exceeding 400 ns,and an equivalent noise at 1k Hz not exceeding 50 n V/√Hz.