A GaAs monolithic linear‐in‐dB wide‐dynamic‐range variable‐gain amplifier with matching compensation for 1.95‐GHz applications

Abstract

This paper describes a method to design a compact linear‐in‐dB variable‐gain amplifier (VGA) with good input/output matching in a wide gain‐control range. The method is theoretically supported and has been validated with the design of a 1.95‐GHz GaAs fully monolithic VGA. Measured maximum gain is 18.8 dB with associated noise figure of 6.3 dB and 40‐dB dynamic range with lower than ±1.5‐dB deviation from linearity, under a low control voltage from −0.4 V to −1.5 V. Good linearity with an output 1‐dB compression of 12 dBm at maximum gain and associated 3rd‐order intercept point better than 22 dBm are also shown. The adjacent channel power ratio (ACPR) was measured at the 1.95‐GHz WCDMA band, showing values better than −48 dBc at 885‐KHz offset and −70 dBc at 1.98‐Mhz offset over the whole control range. The chip size is 2 × 1.0 mm2 and consumes only 34 mA from a supply voltage of 3.5 V. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 251–257, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20602

A 45-dB variable-gain low-noise MMIC amplifier

“…Same is true for the work [4] though here, the achieved gain variation is 16 dB. Work done in [6] claims a gain variation of 40 dB with Max. Gain of 18 dB.…”

“…There are usually four types of VGAs. (1) Current steering technique: The Gilbert Cell topology [1], [2] (2) Variable transconductance topology [3], [4] (3) Using an attenuator (dynamic/discrete) in conjunction with the amplifier [5], [6] (4) Feed back topology (both series and shunt) [7].…”