A 0.9 V wide-input-range bulk-input CMOS OTA for G/sub m/-C filters

Abstract

The G/sub m/-C technique is extensively used for continuous-time filtering applications because it results in tunable, wideband and compact designs. In this paper, an OTA capable of operating at a supply voltage of 0.9 V is proposed using a novel bulk-input differential pair without the use of a tail current source. Good CMRR (63 dB) is still achieved by using the gate terminal to control the total current in the differential pair, via the use of a dummy pair. The OTA also exhibits a wide differential input range of /spl plusmn/ 600 mV and good G/sub m/- tunability. Simulation and test results are also presented with the OTA used in a second order cochlea low-pass filter. For this design, a standard double-poly double-metal CMOS process has been used, having a nominal threshold voltage of around 0.7 V.