0.4-V nW-Power High-Gain Bulk-Driven Two-Stage OTA With Self-Cascode Composite Transistors and Intrinsic Current-Buffer Miller Compensation
Muhammad Omer Shah, Marco Privitera, Andrea Ballo, Massimo Alioto, Salvatore Pennisi
Abstract
This paper presents a 0.4-V bulk-driven two-stage operational transconductance amplifier (OTA) achieving an exceptionally high voltage gain exceeding 120 dB without requiring additional bias voltages. This is accomplished using a self-cascode composite transistor configuration. Common-mode and power-supply rejection ratios ( CMRR and PSRR, respectively) exceeding 90 dB are achieved through input stage optimization. An intrinsic current-buffer Miller compensation technique is also employed to enhance frequency performance. Compared to state-of-the-art designs, the proposed OTA exhibits superior performance in terms of gain-bandwidth trade-off, settling time, PSRR, and robustness against variations. This is demonstrated through extensive measurements across corner wafers and temperature within the range of -20<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>C to 100<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∘</sup>C (unavailable in prior art).