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Accurate dB-Linear Variable Gain Amplifier With Gain Error Compensation

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3 Author(s)
Inyoung Choi ; Department of Electrical Engineering and the Division of Information Technology Convergence Engineering, POSTECH (Pohang University of Science and Technology), Pohang, Korea ; Heesong Seo ; Bumman Kim

This paper describes use of a novel exponential approximation for designing dB-linear variable gain amplifiers (VGAs). The exponential function is accurately generated using a simple error-compensation technique. The dB-linear gain is controlled linearly by the gate voltage, resulting in a simple and robust VGA. The proposed dB-linear VGA fabricated in a 65-nm CMOS process achieves a total variable gain range of 76 dB and dB-linear range greater than 50 dB with ±0.5-dB gain error. Under a 1.2-V supply voltage, the current consumption of the VGA is 1.8 mA and that of the output buffer is 1.4 mA. The input-referred in-band noise density is 3.5 nV/√{Hz} and the in-band OIP3 is 11.5 dBm. Due to the very simple circuit topology, the total active area of the VGA and the output buffer is extremely small, 0.01 mm2.

Published in:

IEEE Journal of Solid-State Circuits  (Volume:48 ,  Issue: 2 )