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This paper investigates modeling of silicon-germanium heterojunction bipolar transistor noise parameters and impedance-matched Low-Noise Amplifiers (LNAs) intended for operation across a wide temperature range (from 93 to 393 K). In general, noise performance improves with cooling until about 150 K, then degrades some because of carrier freeze-out. With a temperature independent bias current, an LNA designed for 300 K operation shows acceptable performance from 93 to 393 K, albeit with some degradation of linearity below 120 K.