Noise-gain tradeoff in RF SiGe HBTs

This work examines the trade-off between noise figure and gain in SiGe HBT RF technology. Based on the linear noisy two-port theory, analytical expressions for the minimum noise figure, the optimum source admittance, and the associated gain are derived. For many current RF applications of SiGe HBTs operating at frequencies comparable to or smaller than f/sub T///spl radic//spl beta/, /spl beta/ must be increased through SiGe profile optimization to further reduce noise. This noise improvement, however, also results in a degradation of associated gain, as experimentally observed. The implications of the noise-gain trade-off for RF integrated circuit design are discussed.