Design of an integrated low power high CMRR instrumentation amplifier for biomedical applications

The objective of this paper is to discuss the advantages and drawbacks of using Trapezoidal Association of Transistors (TAT) in the implementation of a low-power high-CMRR CMOS instrumentation amplifier (IA) aimed for biomedical applications. IAs are well suited for biomedical applications due to its high CMRR. For the sake of comparison, two versions of the circuit were designed, prototyped and characterized. The performance of a version with its current mirrors implemented with TAT, where supposedly higher CMRR could be achievable, is compared to another with single-transistor implementation of current mirrors in order to analyze the CMRR performance. The IA circuit was designed in AMIS 1.5 μm technology and manufactured through the MOSIS Service. In addition to the better performance attained by the classic implementation of the amplifier, with CMRR higher than 120 dB, this version of the IA consumed less than one third of the area from the TAT version. Comparison of both versions from same topology indicates no advantages of using TATs in the current mirrors of this type of IA.