B. E. Boser 1

Advanced Analog Integrated Circuits

Precision Techniques

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

EE240B – Precision Techniques

B. E. Boser 2

Topics

• Offset

• Drift

• 1/f Noise

• Mismatch

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Motivation

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Sources of Inaccuracies in ICs

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Advanced Analog Integrated Circuits

1/f Noise

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

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1/f Noise Spectrum

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1/f Noise

EE240B – Precision Techniques

• Other names: flicker noise, pink noise

• Caused by traps near Si/SiO2 interface– Randomly capture and release carriers– Less significant in BJT, JFET, bulk current flow (PMOS)

• Empirical models:– D. Xie et al., “SPICE Models for Flicker Noise in n-MOSFETs from

Subthreshold to Strong Inversion,” IEEE Trans. CAD, Nov 200, pp. 1293-1303.

– 𝑖# $⁄& =

()*+,-./0

∆$$

• Kf is technology dependent, numbers for EE 240B:

180nm Process 65nm ProcessNMOS 4∙106&7A 9 F 6∙106&7A 9 FPMOS 2∙106&7A 9 F 3∙106&7A 9 F

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1/f Noise Corner Frequency

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1/f Noise Corner Frequency

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“Total” 1/f Noise

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Total 1/f versus Thermal Noise

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MOS Model with Channel Noise Generator

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Other MOSFET Noise Sources

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Advanced Analog Integrated Circuits

Shot Noise(Aside …)

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

EE240B – Precision Techniques

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Shot Noise in PN Junction

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Shot Noise in BJTs

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BJT Small Signal Noise Model

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Advanced Analog Integrated Circuits

Offset

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

EE240B – Precision Techniques

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Modeling Offset

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Sources of Error and Mitigation

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Dynamic Offset Cancellation (DOC)

Refs: [1] K. Makinwa, "Dynamic offset cancellation techniques in CMOS," ISSCC Tutorial, Feb. 2007 (available from SSCS website).

[2] C.C. Enz and G.C. Temes, “Circuit techniques for reducing the effects of opamp imperfections: autozeroing, correlated double sampling and chopper stabilization,” Proc. IEEE, Nov. 1996, pp. 1584 -1614.

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DOC Techniques Comparison

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DOC versus Trimming

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Advanced Analog Integrated Circuits

Auto Zeroing

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

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Auto-Zeroing Principle

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Auto-Zero Phase F1 (DC Analysis)

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Amplification Phase F2 (DC Analysis)

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Advanced Analog Integrated Circuits

Auto Zeroing Noise Analysis

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

EE240B – Precision Techniques

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What Happens to Noise?

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Noise Transfer Function

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Noise Transfer Function

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Noise Spectrum at Output

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Advanced Analog Integrated Circuits

Auto Zeroing Charge Injection

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

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Mitigating Charge Injection Error

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Reducing Charge Injection Error (1)

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Reducing Charge Injection Error (2)

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Multistage Offset Cancellation

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Multistage Offset Cancellation

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Comparator Example

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Comparator Example: Circuit Details

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Auto-Zeroing Residual Offset

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Advanced Analog Integrated Circuits

Chopper Stabilization

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

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Chopping Idea

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Chopping Concept

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Square Wave Modulator

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Time Domain

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Frequency Domain

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Frequency Domain

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Advanced Analog Integrated Circuits

Chopper Noise

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

EE240B – Precision Techniques

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Residual In-Band Noise

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Residual In-Band Noise

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Example

[ Enz 1996 ]

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Two-Stage Chopper Amplifier

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Folded Cascode with Chopper

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Advanced Analog Integrated Circuits

Chopper Nonidealities

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

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Finite Amplifier Bandwidth

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Clock Feedthrough

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Summary of Chopper Design Considerations

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Advanced Analog Integrated Circuits

Advanced Chopping Techniques

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

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Objectives

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Nested Chopping

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[ Bakker 2000 ]

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Spike Dead-Banding

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[ Menolfi 2001 ]

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Spike Bandpass Filter

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[ Menolfi 1999 ]

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Ripple Reduction with AC Coupling

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Ripple Reduction with SC Filter

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[ Bakker 1997 ]

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Ripple Reduction with Digital Filter

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Advanced Analog Integrated Circuits

Chopper Amplifier Performance

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

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Offset Compensated OpAmps

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Implementation Example

http://electronicdesign.com/analog/chopper-stabilized-op-amps

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Chopping Summary

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Advanced Analog Integrated Circuits

Dynamic Element Matching

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

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Application: Precision DAC

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DEM Concept

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DAC Application Example

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Advanced Analog Integrated Circuits

Temperature Sensor Example

Bernhard E. BoserUniversity of California, Berkeley

boser@eecs.berkeley.edu

Copyright © 2016 by Bernhard Boser

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CMOS Temperature Sensor

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[ Pertijs 2005 ]

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Bandgap Temperature Sensing

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Sensor Principle

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A/D Conversion: SD Modulator

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Temperature Sensor Block Diagram

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(1) Accurate 1:p Ratio with DEM

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Sigma-Delta Modulator

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Sigma-Delta Circuit Implementation

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Evaluation

• Other techniques used to get target performance:– 𝛽 insensitive 𝐼@ABC generation– 𝑉@E curvature correction

• Nonlinear decimation filter– 𝑉@E averaging between 𝑄/ and 𝑄G

EE240B – Precision Techniques