RF Circuit Implications of Moderate Inversion Enhanced Linear Region in MOSFETs

The implications for radio frequency circuit design of the nonlinear behavior of a MOSFET transistor over all regions of operation, including moderate inversion region, are investigated. Third-order intermodulation distortion in a MOSFET amplifier is analyzed by means of Volterra Series representation. Analysis and measurements reveal a significant peaking, or "sweet-spot" of the third-order intercept point in the moderate inversion region. As a result, a significant increase in linearity with low power consumption is possible. Analysis and measurements shows the dependance of distortion on the frequency, and transistor parameters, as well as the effects of the load impedance and feedback.