Design of a 0.8 Volt fully differential CMOS OTA using the bulk-driven technique

This paper explores and presents the possible approaches to the design of a low-voltage operational transconductance amplifier (OTA) using the bulk-driven technique. The design of a 0.8 V fully differential folded-cascode OTA using a 0.35 μm CMOS technology having a threshold voltage of 0.6 V is presented. This OTA utilizes bulk-driven differential-pairs to achieve rail-to-rail input operation, and gate- and bulk-biased cascode transistors to increase the output resistance. A continuous-time common-mode feedback (CMFB) is used for this OTA, which implements the bulk-driven differential pairs to sense the common-mode voltage smaller than the transistor´s threshold voltage, as well as bulk-driven current mirrors to reduce voltage headroom consumption. This OTA has been designed using Alcatel´s 0.35 μm twin-well CMOS technology, and the simulation results indicate an open-loop gain>60 dB, unity gain-bandwidth=3.4 MHz with a 5 pF load, and an input common mode range (ICMR) of 0.8 V.