Information Technology Reference
In-Depth Information
A Low-Power Wideband High Dynamic Range
Single-Stage Variable Gain Amplifier
Vivek Verma 1 and Chetan D. Parikh 2
1 vivekverma23@gmail.com
2 Institute of ICT, Ahmedabad University, Ahmedabad, India
chetan.parikh@ahduni.edu.in
Abstract. This paper presents a low-voltage, low-power, wideband, single-
stage variable gain amplifier (VGA) that provides a 57-dB gain variation. It
consumes 1.35 mW, which is one of the lowest power consumptions reported
for similar VGAs in the literature. The 3-dB bandwidth varies from 110 MHz at
25 dB gain to 3.8 GHz at -32 dB gain.
Keywords: Amplifier, analog circuits, CMOS, variable gain amplifier (VGA).
1
Introduction
Variable gain amplifiers (VGAs) are used to maximize the dynamic range of
electronic systems in medical equipment, telecommunication, disc drives and many
other systems where the signal amplitude may experience large variations and hence
requires an inverse change in gain. In communication systems, VGAs play a role in
automatic gain control by sensing the power level of incoming signals and
normalizing the average amplitude of the signal to a reference value.
There are two broad approaches for designing VGAs. One is by analog gain
control [1-6], and the other is discrete gain steps with digital control [7,8]. Digitally
controlled VGAs use binary weighted arrays of resistors or capacitors for varying the
gain, and analog VGAs use a variable transconductance or a variable resistance. An
example application of analog VGAs is in code division multiple access (CDMA)
systems, which require a power control range larger than 80 dB, and a continuously
variable gain is preferred because it avoids signal phase discontinuity [9,10].
In this paper, we propose a single-stage CMOS VGA which uses capacitance
cancellation technique to achieve wideband operation, and a pseudo-exponential
MOSFET circuit with parallel driver and load paths for the dc currents of the
differential amplifier, to achieve a wide dynamic range, and minimized chip area and
power consumption.
 
Search WWH ::




Custom Search