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A $2.1{\sim}2.5\;GHz$ variable gain LNA with a shunt feed-back  

Hwang, Yong-Seok (Information and Communication University)
Yoo, Hyung-Joun (Information and Communication University)
Publication Information
Journal of the Institute of Electronics Engineers of Korea SD / v.44, no.7, 2007 , pp. 54-61 More about this Journal
Abstract
A variable gain low noise amplifier (VG-LNA) implemented in TSMC 0.18 um process is presented. This VG-LNA is designed of two stage amplifier, and its gain is controlled by the shunt feedback loop composed of a gain control transistor (GCT) and a coupling capacitor in second stage. The channel resistance of GCT in the shunt feedback loop influences the input and output stages of a second stage by the Miller effect. Total gain of the proposed VG-LNA is changed by two factors, the load impedance reduction and the interstage mismatch by controlling the channel resistance of the GCT. Consequently, by adding a shunt feedback with a gain control transistor, this proposed VG-LNA achieves both wide gain tuning range of 37 dB and continuous gain control simultaneously.
Keywords
Gain control; LNA; CMOS; shunt feedback;
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