Ultra low-power electronically tunable current-mode instrumentation amplifier for biomedical applications

In this paper, a new current-mode instrumentation amplifier with electronic tuning and low-voltage operation capabilities is presented. Simplicity is other important feature so that the whole circuit is composed of only 20 transistors. All the above have been achieved using MOS transistors biased in the sub-threshold region. The required current-controlled gain stage has been implemented using an appropriate translinear loop which is fed by the output of a current subtraction stage, realized through the employment of flipped voltage follower based current-mirrors. The performance of the presented amplifier is evaluated through simulation results, using the Cadence suite and MOS transistors models provided by the Austria Mikro Systeme 0.35μm CMOS process. The differential gain was 20–40dB, the Common-Mode Rejection Ratio (CMRR) was 44.4–48.9dB, achieved at power dissipation 72.75–386.1nW. The bandwidth was 7 kHz and the Total Harmonic Distortion (THD) was 2% for an input signal with amplitude equal to 550 pA. As an application example, the proposed current-mode instrumentation amplifier has been employed for removing the noise component in electrocardiogram signals.