A new analytical expression of associated gain is derived using linear noisy two-port theory. and used to explain a previous experimental observation of lower (worse) associated gain in SiGe HBTs featuring lower (better) noise. For present RF applications of SiGe HBTs operating at frequencies comparable to or smaller than f(T)/rootbeta, beta must be increased through SiGe profile optimization to further reduce noise. This noise improvement, however. necessarily results in a degradation of associated gain, as experimentally observed. The implications of the noise-gain tradeoff on RF integrated circuit design are discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.