Rail-to-rail differential linear range OTA with pico-A/V transconductance for subHertz OTA-C filter

This paper presents a new configuration of a rail-to-rail subthreshold OTA with very small transconductance suitable for implementing extreme low frequency filter. We exploit the intrinsic property of dc-level translation of multiple input floating gate (MIFG) transistor by serially stacking such devices in diode connected configuration as source degeneration of a subthreshold OTA which achieves simultaneously rail-to-rail differential linear range and very small transconductance. Under 2 V supply voltage, the total harmonic distortion (THD) is less than 1% for 2 Vpp input. The transconductance range is 15-150 pS for a biasing current of 1-100 nA while the total power consumption is kept below 2 μW.