Understanding wide-band MOS transistors

A quantitative understanding of MOS-transistor speed has been slow to emerge because of the absence of a commonly agreed-upon figure of merit for MOS-transistor speed and a lack of familiarity among designers with MOS-amplifier topologies. It is suggested that these problems can be addressed through the use of the unity-gain current frequency (f _T) as a figure of merit for MOS transistors, the use of f_T in the prediction of amplifier bandwidth, and a wider familiarity among designers with practical examples of MOS wideband amplifiers. The use of f_T as a figure of merit is discussed, and the achievable amplifier bandwidths are determined. Increasing the f_T of an MOS device by making the g_m larger or the C_g smaller, or both, is discussed. Wideband CMOS amplifiers are considered