All CMOS Low-Power Wide-Gain Range Variable Gain Amplifiers

Quoc-Hoang DUONG  Chang-Wan KIM  Sang-Gug LEE  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E91-C    No.5    pp.788-797
Publication Date: 2008/05/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e91-c.5.788
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Electronic Circuits
Keyword: 
variable gain amplifier (VGA),  automatic gain control (AGC),  transceiver,  amplifier,  

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Summary: 
Two variable gain amplifiers (VGAs) that adopt new approximated exponential equations are proposed in this paper. The dB-linear range of the proposed VGAs is extended more than what the approximated exponential equations predict by a bias circuit technique that adopts negative feedback. The proposed VGAs feature wide gain variation, low-power, high linearity, wide control signal range, and small chip size. One of the proposed VGAs is fabricated in 0.18 µm CMOS technology and measurements show a gain variation of 83 dB (-3647 dB) with a gain error of less than 2 dB, and P1 dB/IIP3 from -55/8 to -20/20.5 dBm, while consuming an average current of 3.4 mA from a 1.8 V supply; the chip occupies 0.4 mm2. The other VGA is simulated in 0.18 µm CMOS technology and simulations show a gain variation of 91 dB (-4150 dB), and P1 dB/IIP3 from -50/-25 to -33/0 dBm, while consuming an average current of 1.5 mA from a 1.8 V supply.