An instrumentation amplifier (IA) is a very important analog block used in a wide range of application such as: medical instrumentation, read-out circuit of biosensors, data acquisition, and signal processing, where it is necessary to amplify the small differential signals. The key property of these amplifiers is the ability to reject undesired common mode voltages [1]. So that Common-Mode Rejection Ratio (CMRR) is the key parameter to measure the quality of an instrumentation amplifier.