A low voltage wide-input-range bulk-input CMOS OTA

Abstract

The Gm-C technique is extensively used for continuous-time filtering applications because it results in tunable, wideband and compact designs. In this paper, an OTA architecture using a novel bulk-input differential pair without the use of a tail current source is proposed. Good CMRR 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 and good Gm-tunability. For this design, two standard double-poly double-metal CMOS processes were investigated: a 0.8 μm process having a nominal threshold voltage of around 0.7 V and a 0.35 μm process having a nominal threshold voltage of 0.5 V. Simulation results are presented for both designs while test results are presented, for the OTA, implemented using the 0.8 μm process, used in a second order cochlea low-pass filter.