Transcript High-speed Current-based Comparators

High-speed Currentbased Comparators
ECE 1352 Presentation
By: Duy Nguyen
Overview
Introduction to comparators
 Current comparators
 Advanced current comparators
 Conclusions
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Introduction
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Comparators are widely used in many analog
circuits (A/D converters, sensor circuits…)
Voltage comparators can be implemented using
an op amp.
Limitation: speed, offset voltage, power.
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Why current-based comparators?
Low VDD => low power consumption and
compatible with digital circuits.
 Minimum size transistors => small area.
 High speed.
 Many signal sources from sensors are
current-based.
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Simple current comparator
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High output impedance to
amplify small current
difference.
Low operating freq due to
high output impedance.
No compensation for
charge-injection and offset
voltage.
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Advanced current comparator
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Input stage
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Current amplifying stage
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Current to voltage
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Voltage follower
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SR flip flop
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Compensation
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Conclusions
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Current comparators have many
advantages over voltage ones:
 Small
area.
 Low power.
 Potential high speed.
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Future trends:
 Lower
power consumption for portable
wireless applications.
 Higher accuracy and speed.
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References
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[1] H. Traff – “Novel Approach To High Speed CMOS Current Comparators” – Electronics
Letters, Vol. 28 No. 3, January 1992.
[2] G. Palmisano, G. Palumbo – “High performance CMOS current Comparator Design” –
IEEE Trans. Circuits Sytem II, vol.43, pp. 785-790, December 1996.
[3] R. Rio-Fernandez, G. Linan-Cembrano, R. Dominguez, A. Rodriguez-Vazquez, “A
Mismatch-Insensitive High-Accuracy High-Speed continuous -time Current Comparator in
Low-Voltage CMOS” – Proc. Analog and Mixed IC Design, 1997.
[4] L. Chen, B. Shi, C. Lu – “A High Speed/Power Ratio continuous-time CMOS current
Comparator” – Conf. Electronics, Circuits and Systems, 2000.
[5] L. Luh, J. Choma, J. Draper – “A high-speed High-resolution CMOS Current
Comparator” – Proc. ICECS, Vol. 1999.
[6] David A. Johns, Ken Martin – “Analog integrated circuit design” – John Wiley & Sons,
1997
[7] M. Bracey, W. Redman-White, J. Richardson, J. Hughes – “A full Nyquist 15 MS/s 8-b
Differential Switched-Current A/D converter” – IEEE JSSC, Vol. 31 No. 7, 1996.
[8] A. Worapishet, J. Hughes, C. Toumazou – “Speed and Accuracy Enhancement Techniques
for high performance Switched-Current Comparators” – IEEE JSSC, Vol. 36 No. 4, 2001.
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