Frequency Responses of Noise Figure and Input Matching for Low-Noise Amplifier Design
A method for optimizing a low-noise amplifier (LNA) with understanding Frequency responses of its noise figure
(NF) and input matching characteristics is introduced. By determining the quality factors (Q-factors) of the NF (Qnf) and the
input matching network (Qin), the NF and input return loss (S11) frequency response of an LNA are controlled. According to
different purposes such as narrowband or wideband LNAs, the Q-factors should be chosen properly. Medium-Qnf and high-Qnf
cascode LNAs in CMOS technologies has been implemented for verifying validity of the proposed theory.
Index Terms- Noise figure, input matching, CMOS, low-noise amplifier, quality factor.