Study on Transfer Characteristics of MOSFET Operating in Weak Inversion Region

Abstract

In order to compensate non-linearity of any electronic devices, we have proposed small scale exponentiation conversion circuit by utilizing subthreshold operation of the MOSFET up to now. The exponentiation conversion circuit multiplies the logarithmically converted input signal by the power exponent value to perform exponential conversion. The power supply voltage of the power conversion IC has been reduced to 3.3V, however, the characteristics of the MOSFETs have changed with the lower voltage. Also, since the performance of the exponentiation conversion IC is determined by the exponential and logarithmic conversion accuracy of the signal in subthreshold operation, the current density and bias conditions of the MOSFET must be carefully designed. In this paper, we report the details of the MOSFETs’ optimum operating conditions, which were established by detailed analysis of the signal dynamic range, subthreshold leak current and subthreshold swing in the subthreshold region of the MOSFETs when the source voltage, supply voltage and Temperature are varied.