Abstract
Low-power cryogenic low-noise amplifiers (LNAs) are desired to ease the cooling requirements of ultra-sensitive cryogenically cooled instrumentation. In this paper, the tradeoff between power and noise performance in silicon–germanium LNAs is explored to study the possibility of operating these devices from low supply voltages. A new small-signal heterojunction bipolar transistor noise model applicable to both the forward-active and saturation regimes is developed from first principles. Experimental measurements of a device across a wide range of temperatures are then presented and the dependence of the noise parameters on collector–emitter voltage is described. This paper concludes with the demonstration of a high-gain 1.8–3.6-GHz cryogenic LNA achieving a noise temperature of 3.4–5 K while consuming just ${\hbox{290}}~\mu{\hbox{W}}$ when operating at 15-K physical temperature.
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