A 380-MHz CMOS Linear-in-dB Variable Gain Amplifier with Gain Compensation Techniques for CDMA Systems

Osamu WATANABE  Mitsuyuki ASHIDA  Tetsuro ITAKURA  Shoji OTAKA  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E86-C   No.6   pp.1069-1076
Publication Date: 2003/06/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Devices and Circuits for Next Generation Multi-Media Communication Systems)
Category: 
Keyword: 
variable gain amplifier,  VGA,  gain compensation,  temperature compensation,  linear-in-dB characteristics,  square circuit,  MOSFET,  square-law region,  exponential-law region,  CDMA,  

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Summary: 
A linear-in-dB VGA of the current-divider type is fabricated in 0.25 µm CMOS technology. Two gain compensation techniques are proposed in order to compensate the gain deviations due to a MOSFET which has a square-law characteristic or an exponential-law characteristic determined by its current density. Temperature compensation techniques are also proposed. Measure results obtained at 380 MHz are a gain range of 80 dB, a gain error of 3 dB, and an NF of 11 dB.