New Realization of Quadrature Oscillator using OTRA

Abstract

In this paper a new, operational transresistance amplifier (OTRA) based, third order quadrature oscillator (QO) is presented. The proposed structure forms a closed loop using a high pass filter and differentiator. All the resistors employed in the circuit can be implemented using matched transistors operating in linear region thereby making the proposed structure fully integrated and electronically tunable. The effect of non-idealities of OTRA has been analyzed which suggests that for high frequency applications self-compensation can be used. Workability of the proposed QO is verified through SPICE simulations using 0.18μm AGILENT CMOS process parameters. Total harmonic distortion (THD) for the proposed QO is found to be less than 2.5%. The sensitivity, phasenoise analysis is also discussed for the proposed structure. Keyword:OTRA Phasenoise Quadrature oscillator Sensitivity THD Copyright © 2017 Institute of Advanced Engineering and Science.All rights reserved. Corresponding Author:Gurumurthy Komanaplli , Department of Electronics and communication Engineering, Delhi Technological University, Bawana Road, New Delhi, India-110085. Email: murthykgm@gmail.com INTRODUCTIONIn last few decades current-mode (CM) processing has evolved as a promising design technique to provide efficient solutions to circuit design problems. This evolution has resulted in emergence of numerous CM analog building blocks [1].The operational trans resistance amplifier (OTRA) is one among these blocks. It is a high gain current input, voltage output amplifier [2] and uses current feedback technique which makes its bandwidth almost independent of the closed loop gain. Additionally it is free from the effect of parasitic capacitances at the input due to virtually internally grounded input terminals [2] and hence non-ideality problem is less in circuits implemented using OTRA.Quadrature oscillators (QO) are an important class of circuits and find wide application in communication, power electronics and instrumentation. This has led a consistent research effort towards second order QO design using wide variety of active blocks, as is evident from vast literature available [2][3][4][5][6][7][8][9][10][11][12][13][14] .It is well known that higher order networks, provide better accuracy, frequency response and distortion performance [15][16][17] as compared to lower order circuits. Owing to this in recent past few third order QO designs [15], [16], [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] have been reported. Realizing sinusoidal oscillator using closed loop with positive feedback is a well-established method. A careful observation suggests that all the reported third order QO designs are based on forming closed loop using combinations of lossy and/or lossless integrators. In this paper a new OTRA based third order QO is proposed that adapts the scheme of using second order high pass filter and a differentiator in a feedback loop [32].A comparative statement of the proposed structure with previously reported QO circuits is reco...

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