A low-power 75dB digitally programmable CMOS variable-gain amplifier

TitleA low-power 75dB digitally programmable CMOS variable-gain amplifier
Publication TypeJournal Article
Year of Publication2007
AuthorsRahmatian, B., and S. Mirabbasi
Journal2007 Canadian Conference on Electrical and Computer Engineering, Vols 1-3

A monolithic low-power digitally programmable variable-gain amplifier (VGA) with a gain range of 75dB is presented. The core of the design is based on a low-distortion source-degenerated differential amplifler structure. The gain is varied by changing the source-degeneration resistor as well as tuning the resistors in the common-mode feedback circuitry. The overall VGA consists of three gain stages. As a proof of concept, a 24dB single gain stage with 2dB gain steps is fabricated in a 0.18 mu m CMOS technology. Based on the measurement results of the prototype chip, the performance of the gain stage is optimized and a three-stage 75dB VGA is designed and simulated. The overall gain can be varied from -15dB to 60dB in 2.5dB gain steps. The bandwidth of the multi-stage VGA is higher than 140MHz and the gain error is less than 0.3dB. The overall VGA draws 6.5mA from a 1.8V supply. The noise figure of the system at maximum gain is 12.5dB, and the IIP3 at minimum gain is 14.4dBm.

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