A design of a low-transconductance linear transconductor utilizing body effect for low frequency applications

For medical devices, low frequency applications are required. Thus, a transconductor which has a very low transconductance is needed. A conventional low-power and low-transconductance transconductor has a problem that a linear input range is narrow for the medical use. This paper proposes an improved local-feedback MOS transconductor operating in subthreshold region utilizing body effect. The proposed transconductor is optimally designed using Newton-Raphson method and Downhill simplex method. The characteristics of the proposed transconductor are confirmed by simulation under the condition that the transconductance is lower than 1 μS. The 1% linear input range is around 100 mV. The THD is around -40 dB for the amplitude of the input voltage is 170 mV under the condition that the frequency of the sinusoidal input voltage is 100 Hz. The simulation results show validity and availability of the proposed transconductor.