A Digitally-Controlled Variable Gain Amplifier (VGA) for Ultra-Wide Band (UWB)

Ting Chang, Hsin-Han Huang, Abhishek Mitra

A CMOS variable gain amplifier (VGA) intended for ultra-wideband system applications will be designed and implemented during the course of the project. The emphasis would be on achieving a 3 dB bandwidth of 528 MHz or greater and at the same time achieving wider gain variation characteristics. The circuit would employ a Gilbert cell with diode connected loads to provide linearly varying gains. We plan to implement a digital scheme for controlling the gain of the VGA as opposed to an analog one. In addition, a Common Mode Feedback is applied in order to stabilize the common-level and thus the gain. If the need arises, we would be implementing bandwidth extension loads to increase the bandwidth of the circuit. A .25 um CMOS process will be used for simulations of the project and the schematic and layout would be done using Cadence.

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