A high DC-gain modified CMOS OTA

Abstract

A new operational transconductance amplifier (OTA) based on the conventional triple folded cascode (TFC) structure is presented. Using the proposed method, the DC gain enhances by adding only three positive feedback devices to the TFC structure. The simulation results for the designed OTA in a typical 0.35μm CMOS technology show 20dB DC gain enhancement of conventional TFC while bandwidth, output voltage swing range, and the phase margin of conventional TFC are not affected. Higher linearity in the larger output voltage swings is the other advantages of proposed approach in comparison to previously reported positive feedback methods.Index Terms-positive feedback device (PFD); linearity; triple folded cascode; dc-gain INTRODUCTIONOperational amplifier is one of the basic and important circuits which has a wide range of applications in several analog circuits, such as filters and data converters, etc. The rapid demand for high speed and high resolution applications such as ADCs and DACs results in an increasing demand for high speed and high gain OTAs. For high-accuracy circuits, OTAs with very high open loop gain and high unity gain frequency are required in order to meet both accuracy and fast settling requirements. Satisfying both of these requirements is difficult with short-channel CMOS processes, since the intrinsic gain of the devices is limited. The new structure proposed in this paper is based on the conventional TFC amplifier. TFC amplifiers have been used in several applications especially where the lower output voltage swing range is not an important factor (e.g. [1]). To increase the dcgain of the TFC amplifier a new method is introduced that uses positive feedback and bulk amplification concepts.

Performance parameters optimization of CMOS analog signal processing circuits based on smart algorithms

“…[20] 48.8 9.32 ----------0.089 4.88 0.5 Pereira-Arroyo et al [44] ---------------3.676 -----0. 1443 -----Laajimi et al [45] 57 55 62° 0.1 -----2.27 -----Bakawale et al [30] ----------55° -----0.025 14.2 -------Lee et al [46] 87 485 70° -----------8 0.35 Yodtean [37] 76 423 86° -----0.4 0.00458 0.18 Mirković et al [47] 57. --------1.12 -----25 14.2 Broomandnia et al [31] -----0.18 ±0.6 -----0.006 0.191 Gajjar and Patel [32] -----0.18 1.8 4 -----0.070 M'Harzi et al [52] -----0.35 ±1.5 100 -----1.28 Garbaya et al [53] RBF-PSO -------------------------Yakout and Alawadi [54] -----0.8 ±2.5 300 -----4.86 Lberni et al [55] NSGA II and MOGA 0.…”