Date of Graduation

5-2012

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering (MSEE)

Degree Level

Graduate

Department

Electrical Engineering

Advisor

H. Alan Mantooth

Committee Member

Randy Brown

Second Committee Member

Scott Smith

Abstract

This thesis presents the design, simulation, layout and testing results for a dB-linear, high dynamic gain range CMOS variable gain amplifier (VGA). The design adopts a new approximated exponential equation called the pseudo exponential equation to implement the dB-linear function. The proposed VGA is designed to have an extremely wide gain variation, small chip area, low supply voltage, and controllable dynamic gain range. The gain variation of the 3-stage VGA is implemented by a voltage to current converter. It controls the bias currents of each VGA cell, so that the output gain of each cell can be controlled. In order to stabilize the output common mode voltage of each VGA cell under the variation of its bias currents, a common mode feedback circuit is introduced in the VGA. The VGA was fabricated in IBM's CMRF8SF 130 nm CMOS process.

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