MOSFET 1/f noise measurement under switched bias conditions

Klumperink et al, have recently had a number of publications on the low frequency noise of MOSFETs under switched gate bias conditions. Since this is an important consideration in the low frequency noise in analog circuits with switching, we have investigated the signal processing technique used in some detail with respect to the data presented in the IEEE Electron Device Letters (vol.2, no.1, p. 43-46, 2000). No consideration was given to phase noise, a mixing with and modulation of the switched bias drain current by 1/f noise, in the analysis of the data. This can result in a response on the spectrum analyzer which corresponds very closely to the experimental data where the switched bias off gate voltage is near the threshold voltage. At low frequencies there will be just 1/f noise, then a plateau caused by the sum of 1/f noise and phase noise, a peak corresponding to the fundamental component of the switched bias, and at higher frequencies a phase noise in excess of the 1/f noise.