Transconductance enhancement in bulk-driven input stages

This paper presents two different circuit techniques which rely on partial positive feedback to enhance the effective transconductance of a CMOS bulk-driven input stage, thus leading to improved values for the DC gain and the gain-bandwidth product. The first approach modifies the conductance of the active load, while the second solution acts directly on the input differential pair of the transconductor. The suitability of the presented techniques is demonstrated by the design of operational transconductance amplifiers operating at two different supply voltages, i.e., 2.4 V and 1.0 V, in standard 0.35-mum CMOS technology. Simulated results are given.