Noise characterization and modeling of polysilicon emitter bipolar junction transistors at microwave frequencies

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Abstract
Microwave noise parameters of polysilicon emitter bipolar junction transistors with emitter areas A E ranging from 3.2 μm2 to 144 μm2, collector current densities J C from ∼7.8×10−5 mA/μm2 to ∼0.31 mA/μm2, and for frequencies between 1 and 5.4 GHz, have been measured and modeled from a 0.8 μm BiCMOS process. Our results show that the minimum noise figure NFmin at the typical working J C of ∼0.16 mA/μm2 and frequency of 1 GHz varied as A −0.26 E , the real R S,OPT and imaginary X S,OPT parts of the optimal source impedance varied as A −0.7 E and A −1 E respectively, the noise resistance R N varied as A −1 E , and the noise voltage V N varied as A −0.41 E . These noise parameter variations with A E are in first order agreement with a simple noise model of the bipolar transistor, and with the experimental finding of the variation of the base resistance R B ∼A −0.92 E and the emitter junction capacitance C JE ∼A −1 E . The detailed modeling of NFmin, NF50 (referenced to a 50 Ω input), and R N as a function of J C and frequency showed good agreement with the experimental results.

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