Analysis and Design Procedure of a Novel Low Power Highly Linear Operational Transconductance Amplifier

Abstract

In this paper, a new highly linear operational transconductance amplifier (OTA) is presented. Proposed OTA employs two linearization techniques of cross-coupled double differential pairs and resistive source degeneration to achieve highly linear response under low power consumption. Considering the linearity and the frequency response issues as main parameters of OTA in the communication circuits, design procedure is theoretically formulated for the best linearity and optimum frequency compensation. Proposed OTA is simulated in 0.18-μm TSMC CMOS technology by Hspice simulator. While, the power consumption is only 467 μW, applying two-tone input voltage with amplitude of 0.6 Vp-p at 10 MHz frequency results in -61 dB third-order intermodulation (IM3) distortion of the output current that still remains below -44 dB for amplitudes up to 1 Vp-p. A precise frequency response analysis is performed which has resulted in optimum values of resistor and capacitor for miller compensation. Using common mode feedback in both stages and push-pull based output stage lead to 108 dB CMRR at DC that decreases to 84.5 dB at 100 kHz frequency.