The relevance of f/sub T/ and f/sub max/ for the speed of a bipolar CE amplifier stage

Generalized expressions for the speed of a CE amplifier stage and a CML gate are derived. They are valid for an arbitrary division of R/sub b/ and C/sub bc/ into internal and external components, and presented in terms of directly measurable transistor parameters (f/sub T/, f/sub max/ and f/sub v/) instead of the conventional sum of RC products. It is shown that the transistor input bandwidth f/sub v/ is an important figure of merit, whereas the maximum oscillation frequency f/sub max/ is only of minor importance for high-speed low-power applications.