Design and performance of small-signal microwave transistors

Abstract

Recent advances in microwave transistor technology, including 1 μm mask resolution, arsenic diffused emitters, and low-resistance contacts compatible with shallow junctions, have resulted in significant improvements in the high-frequency performance of small-signal npn bipolar silicon transistors. These improvements are described and, in particular, the high-frequency performance of arsenic diffused emitter and phosphorus diffused emitter devices are compared in detail in terms of ƒ T, ƒ max , noise figure and available power gain. The effect of collector thickness and doping on ƒ T and ƒ max is discussed and experimental results are compared with computed values. By suitable choice of collector thickness and doping either ƒ T or ƒ max may be optimized: ƒ T = 15 GHz and ƒ max = 26 GHz have been observed. The minimum noise figure is found to be independent of collector thickness and a typical noise figure of 4 dB at 4 GHz is obtained.