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A new design of a linear local-feedback MOS transconductor for low frequency applications

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Abstract

For medical devices, low frequency and low power applications are required, and a transconductor which has a low transconductance is needed. A conventional current division scheme for the low transconductance wastes operating current. This paper proposes an improved local-feedback MOS transconductor operating in subthreshold region. The proposed transconductor is optimally designed using maximally flat approximation method, Newton-Raphson method, and Downhill simplex method. From the optimization, two optimum values are obtained. Characteristics of the proposed transconductor are confirmed by simulation. Transfer characteristics of the proposed transconductor are linear, and the power consumption of the proposed transconductor is 1/60 as compared with the presented transconductor using current division scheme. The CMRR is around 70 dB, and the THD is lower than −55 dB under a condition of that the frequency of the sinusoidal input is 100 Hz. As a demonstration of an application, the proposed transconductor is applied to a low frequency second order Butterworth filter. A cutoff frequency of the filter is 100 Hz. Simulation results show validities and availability of the proposed transconductor.

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Authors and Affiliations

  1. Department of Applied Physics, National Defense Academy, 1-10-20, Hashirimizu, Yokosuka, 239-8686, Japan

    Takeshi Ohbuchi & Fujihiko Matsumoto

Authors
  1. Takeshi Ohbuchi
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  2. Fujihiko Matsumoto
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Correspondence to Takeshi Ohbuchi.

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Ohbuchi, T., Matsumoto, F. A new design of a linear local-feedback MOS transconductor for low frequency applications. Analog Integr Circ Sig Process 75, 257–266 (2013). https://doi.org/10.1007/s10470-012-0006-6

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  • DOI: https://doi.org/10.1007/s10470-012-0006-6

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