In this paper a new approximation is presented for the nonlinear relationship between the gate-to-source voltage and the current of a diode-connected NMOSFET. Using this expression closed-form expressions are obtained for the DC and the amplitudes of the fundamental, secondand third-harmonic and intermodulation components of the gate-to-source voltage resulting from exciting the diodeconnected NMOSFET by a DC biasing current plus a superimposed multisinusoidal EMI. Comparison between calculated and simulated results is included.