Gain and Phase-Improved Substrate-Biased Multi-Gate Based OTA Using Quasi-Compensation Technique
Aditya Raj and Shyam Akashe
A multi-gate OTA using substrate-biasing and quasi-cascode compensation has been demonstrated in this research paper. The quasi-cascode compensation provides a current-adaptive design of multi-gate OTA which ensures high stability by improving phase shift. In this research paper along with the quasi-cascode compensation substrate-biasing technique is also anticipated which maximizes the gain of the multi-gate OTA. The methodology discussed does not affect the output-voltage fluctuation and consumes minimum power. In this research paper OTA is designed by using multi-gate technology and four multi-gate OTA models are presented by applying the anticipated substrate-biasing and quasi-cascode compensation which operate at 0.8V power supply in a 45nm process. The obtained results are compared with previously proposed conventional miller compensation circuit. The aspect ratio of all the transistors used in the multi-gate OTA is equal in size . The miller capacitance used in all the anticipated design is same. The result achieved after simulation of the anticipated models of multi-gate OTA (makes use of both the substrate-biasing technique and Quasi-cascode compensation) clearly verifies that the gain is increased by a factor of 5(14dB), the gain-bandwidth product frequency is enhanced by 50 % as compared to the previously proposed conventional miller-compensation circuits. The phase-margin of the proposed multi-gate OTA has maintained a constant phase margin for multi-gate two stage operational amplifier by varying in its bias current by a factor of 500 (5 to 2500 nA). The Opamp circuit is designed in 45nm CMOS technology and for the result and simulation the proposed design is simulated in Cadence Virtuoso tool with 0.8V power supply.
Keywords: Folded-cascode Compensation, Substrate-Bias, Multi-gate OTA, Compound-transistor Pair