Temperature insensitive current-mode CMOS exponential function generator and its application in variable gain amplifier

A new CMOS current-mode circuit to produce the exponential function, y=exp(x), is proposed. The proposed design has large input and output dynamic ranges while keeping very small linearity error. The functionality of the proposed design, confirmed using Tanner tool with 0.35μm CMOS process technolog...

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Bibliographic Details
Published in:Microelectronics 2014-03, Vol.45 (3), p.345-354
Main Authors: AL-Tamimi, Karama M., AL-Absi, Munir A., Abuelma'atti, Muhammad Taher
Format: Article
Language:English
Subjects:
Amplifiers
Approximation
CMOS
Current-mode
Errors
Exponential
Exponential functions
Generators
Linear-in-dB
Linearity
Noise levels
Translinear principle
Variable gain
VGA
Weak inversion
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Summary:A new CMOS current-mode circuit to produce the exponential function, y=exp(x), is proposed. The proposed design has large input and output dynamic ranges while keeping very small linearity error. The functionality of the proposed design, confirmed using Tanner tool with 0.35μm CMOS process technology indicates that it has superior performance compared to previously reported designs. A nearly 96dB output dynamic range is obtained with the linearity error less than ±0.5dB over an input range −5.75≤x≤5.75. The change in the output current due to temperature variation is ±1.27dB over 100°C range. Application of the proposed exponential function generator in the design of an exponentially controlled variable gain amplifier is presented and its functionality is confirmed using simulation. 71 Linear-in-dB variable gain was achieved. The dB gain is controlled linearly by the control current, resulting in simple and low power structure.
ISSN:1879-2391
0026-2692
1879-2391
DOI:10.1016/j.mejo.2013.12.010