This paper models the time domain and frequency domain characteristics of the noise spectrum of a MOSFET device under varying EMI conditions. The theoretical results are compared with experimental measurements. Both sets of results reveal that the magnitude of the EMI-induced noise is governed by the pulse height, the output load, the parasitic capacitance, the interference frequency and the interference amplitude. Furthermore, it is shown that a higher interference amplitude or frequency increases the harmonic noise. The theoretical method presented in this paper provides a convenient means of evaluating the EMI effects and signal-to-noise ratio (SNR) of MOSFETs and similar wavelength devices. (C) 2008 Elsevier Ltd. All rights reserved.