Design of Instrumentation Amplifier and Buffer for Biomedical Applications Using 180 nm Technology

This paper presents a high-performance Op-Amp based CMOS Instrumentation Amplifier (IA) and a Buffer for biomedical signal applications. This Instrumentation Amplifier is constructed using three two stage operational amplifiers. To achieve the desirable gain for this instrumentation amplifier the aspect ratios and passive resistances of op-amps are selected very carefully. To obtain a required common mode rejection ratio (CMRR) and gain, the appropriate selection of the transistor sizing and op-amp circuit topology were essential for the design of IA for biomedical applications. A voltage buffer amplifier is cascaded with this IA. Voltage follower or buffer circuit is generally used to isolate different stages from each other. The gain and CMRR of two stage amplifier are 60.917 and 81.012 dB respectively. The CMRR and overall differential gain of this IA are 111.21 and 67.41 dB respectively. The total power absorbed by this IA is 368 µW.