A 10-Gb/s inductor-less variable gain amplifier with a linear-in-dB characteristic and DC-offset cancellation

Abstract

This paper presents a broadband inductor-less variable gain amplifier (VGA) with a linear-in-dB gain control characteristic and DC-offset cancellation. The proposed VGA is composed of a variable gain block, an exponential voltage generator, a DC-offset canceller with common-mode voltage correction, and a gain peaking block. To achieve the broad band and reduce the chip area, the gain peaking block employs an inductor-less gain peaking scheme to compensate the high frequency gain drop of the variable gain block and the DC-offset canceller. The VGA fabricated in 0.13 μm SiGe BiCMOS technology achieves a 3-dB bandwidth of 7.5 GHz and a variable gain range from −10 to 30 dB. Due to the inductor-less design, the die area is only 0.53 × 0.27 mm^2 which is the smallest among other similar reported works. At 10-Gb/s, the VGA consumes 50 mW power from a single 1.2 V supply and exhibits an output data jitter of less than 30 pspp.