Folded cascode OTA with improved output voltage range

摘要

A fast-settling operational transconductance amplifier comprises folded-cascode sections A1,A2,B1,B2 (see figures 2 and 3) in which the cascoding effect is enhanced by amplifiers in each section. The amplifiers comprise level shifters 14 at their input so that the cascode nodes SX,SY and the output nodes ON,OP can be at levels near each rail. The OTA may be used in a bandpass Sigma-Delta filter, a digital car radio, or a GSM mobile handset. The OTA uses complementary NMOS and PMOS differential input stages.