Rail-to-Rail, Reconfigurable Subthreshold Bulk-Driven OTA Based on Flipped Voltage Follower for Biomedical Applications

This paper addresses flipped voltage follower (FVF) based two-stage low power cascode compensated operational transconductance amplifier (OTA), functioning in the sub-threshold region. This circuit utilizes a bulk-driven source degenerated along with partial positive feedback (PPF) in (FVF) differential pair of the core circuit, ensures rail-to-rail operation at both input/output, and also enhances the effective bulk transconductance of the core. The proposed OTA uses cascode frequency compensation technique rather than Miller single capacitor compensation to improve the stability and gain bandwidth. This circuit of OTA is operated at a single 0.5V supply voltage and consumes only 100.2nW power to provide about 100 dB entire gain and 17.874 kHz gain-bandwidth product and also produces a high CMRR of 132.1dB. Simulation of the proposed circuit is executed through Cadence Virtuoso software tool using UMC 180nm CMOS process technology. The presented OTA results in low input-referred noise, which is 0.9108 µV/ sqrt (Hz) at 1 kHz and consumes less power, which shows that it is appropriate for biomedical applications.