A hybrid-mode bulk-driven folded cascode OTA with enhanced unity-gain bandwidth and slew rate

A hybrid-mode bulk-driven folded cascode OTA with the enhanced unity-gain bandwidth and slew rate is presented in this paper. To achieve a faster large-signal transient response, a hybrid-mode output stage composed of a traditional folded cascode and an additional current mirror output stage is proposed. The proposed hybrid-mode output stage activates the additional current mirror output stage to produce a large transient charge/discharge current when slewing happens, overcoming the issue of limitation of folded current source in traditional folded cascode structure. By the combination of super bulk-driven input stage and proposed hybrid-mode output stage, not only does the bulk-driven folded cascode OTA achieve a large unity-gain bandwidth and high dc gain, but also the large-signal transient response is significantly improved. Designed under SMIC 0.18 μm process, simulation results demonstrate that the proposed bulk-driven OTA achieves 2 times the unity-gain bandwidth and 12 times the slew rate of conventional counterpart at the same power dissipation.