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not-yet-known not-yet-known not-yet-known unknown Evolution of and Perspectives on Differential-Pair-Based CMOS Variable Gain Amplifiers with Linear-in-Decibel Gain Control: A Tutorial
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  • Siqi Wang,
  • Zhenghao Lu,
  • Zhong Tang,
  • Xiaopeng Yu,
  • Hanming Wu,
  • Kiat Yeo,
  • Yong Chen
Siqi Wang
Zhejiang University College of Information Science and Electronic Engineering
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Zhenghao Lu
Soochow University School of Electronic and Information Engineering
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Zhong Tang
Vango Technologies
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Xiaopeng Yu
Zhejiang University College of Information Science and Electronic Engineering
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Hanming Wu
Zhejiang University
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Kiat Yeo
Singapore University of Technology and Design Engineering Product Development
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Yong Chen
Tsinghua University Department of Electronic Engineering

Corresponding Author:[email protected]

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Abstract

not-yet-known not-yet-known not-yet-known unknown A variable gain amplifier (VGA) is an essential building block used in the automatic gain control (AGC) loop to provide a continuous, adjustable gain for the signal strength. To maintain the stability and consistency of the AGC loop, it is necessary to ensure that the gain of the VGA has an accurate dB-linear characteristic. This tutorial provides a detailed overview of the development of dB-linear VGAs based on differential pair structures over recent years. We categorise various VGA cells based on differential pair structures, analyse their operating principles, and explain the key features of each topology. Based on observation and extraction of the dB-linear implementation schemes used by these VGAs, we summarise three basic methods for achieving dB-linear gain control. We also discuss specific methods for realising the exponential function, using a true exponential and a mathematical approximation, and present the different types of approximation functions adopted in the works described here. Considerations in regard to the tuning range, gain error, bandwidth, linearity, process-temperature robustness, and circuit simplicity are also discussed. Finally, we draw comparisons and give perspectives for future dB-linear VGAs.
Submitted to International Journal of Circuit Theory and Applications
16 Jun 2024Review(s) Completed, Editorial Evaluation Pending
26 Jun 2024Reviewer(s) Assigned
20 Aug 2024Editorial Decision: Revise Minor
24 Aug 20241st Revision Received
27 Aug 2024Submission Checks Completed
27 Aug 2024Assigned to Editor
27 Aug 2024Review(s) Completed, Editorial Evaluation Pending
27 Aug 2024Reviewer(s) Assigned
27 Sep 2024Editorial Decision: Accept