for the biomedical instrumentation amplifier in order to raise cmrr a biomedical signal level conversion circuit 10 is connected to a first voltage to current operation amplifier 11 and a second voltage to current operation amplifier 12 the first voltage to current operation amplifier 11 and the second voltage to current operation amplifier 12 are structured with voltage operation amplifiers 111 and 121 that are connected to current mirrors 112 and 122 for replacement of resistors as passive elements and convert input voltage into current of which a signal is amplified by a differential amplifier 13 thus the amount of resistors and thermal noise may be reduced and the variation errors of the resistances in a manufacturing process may further be reduced also with the accuracy of the current mirrors the capability of matching to circuits is enhanced thereby the performance of cmrr and psrr increasing fig4 is a diagram of a level conversion circuit for the biomedical signal processing when an electrode pad senses a weak biomedical signal and connects to two input terminals of v 1 and v 2 the signal varies at a dc level of around 0v because pmos accepts a negative voltage below 0v after the conversion of voltage level the voltage levels of v 1 and v 2 are raised to vin and vin u2212 higher dc levels so as to drive and use an input common mode level of an improved instrumentation amplifier further i o transistors are structured with pmos since pmos.