Power-efficient analog design based on the class AB super source follower

SUMMARY A class AB version of the conventional super source follower (SSF) is described. The circuit greatly increases slew rate (SR) and current efficiency, maintaining the low distortion and low output resistance of the SSF. Class AB operation is achieved without extra power dissipation or supply...

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Bibliographic Details
Published in:International journal of circuit theory and applications 2012-11, Vol.40 (11), p.1143-1163
Main Authors: Lopez-Martin, Antonio J., Acosta, Lucia, Garcia-Alberdi, Coro, Carvajal, Ramon G., Ramirez-Angulo, Jaime
Format: Article
Language:English
Subjects:
analog CMOS circuits
class AB amplifiers
low-voltage CMOS circuits
quasi-floating-gate MOSFET
super source follower
transconductors
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Summary:SUMMARY A class AB version of the conventional super source follower (SSF) is described. The circuit greatly increases slew rate (SR) and current efficiency, maintaining the low distortion and low output resistance of the SSF. Class AB operation is achieved without extra power dissipation or supply requirements, and without bandwidth or noise degradation. The circuit can advantageously replace the SSF in a wide variety of analog systems, opening a new research line in analog design. To illustrate the widespread application of this cell, a class AB differential unity‐gain buffer, a class AB differential current mirror and two class AB differential transconductors are designed, fabricated in a 0.5µm CMOS technology and tested. Measurement results using a dual supply of ±1.65V show that the proposed class AB version of the SSF improves SR by a factor 21.5 and increases bandwidth by 10%, keeping noise level, input range, power consumption, and supply requirements unaltered. The fabricated class AB current mirror features a THD at 100 kHz of − 62dB for signal currents 20 times larger than the bias current. The fabricated transconductors feature an IM3 at 1 MHz of − 56.6dB for output currents more than 13 times larger than the bias currents. Copyright © 2011 John Wiley & Sons, Ltd. A new technique for low‐voltage power‐efficient analog design is presented, based on a class AB version of the Super Source Follower as basic building block. Measurement results of various applications (buffers, current mirrors and transconductors) confirm the advantages of the proposed technique. Copyright © 2011 John Wiley & Sons, Ltd.
ISSN:0098-9886
1097-007X
DOI:10.1002/cta.776