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Operational Transconductance Amplifier (OTA) in 45nm CMOS
Jie Wang
Ming Hsieh Department of Electrical Engineering
University of Southern California, Los Angeles, CA 90089
December 3, 2014
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Your Name EE 536a Final Project Presentation December 3, 2014
Statement of the problem: High Performance OTA
Main challenges:
Large Range of Vin,
100GHz ππ’5000V/us Slew Rate
General approach:
Two Amplifiers + MUX
Pole Cancelling
Large Current, Smaller Cc
Introduction
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Your Name EE 536a Final Project Presentation December 3, 2014
Block Diagram
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Your Name EE 536a Final Project Presentation December 3, 2014
Step1: Fix current
Step 2: Fix gain
Step 3: Calculate required ππ
Step 4: Test uπΆππ₯
Find π
πΏ
General Design Strategy
gm= 2π’πΆππ₯π
πΏπΌπ
ππ =1
ππΌπ
Gain = gm(πππ//πππ)
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Your Name EE 536a Final Project Presentation December 3, 2014
How to Find uπΆππ₯
Betaeff =uπΆππ₯π
πΏ
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Your Name EE 536a Final Project Presentation December 3, 2014
NMOS Based Input Stage Amplifier
π1 β1
ππ2πΆππ 1π 2
π2 βππ2πΆπΆπΆπΆπΆ2
=ππ2
πΆ2
π΄π·πΆ = ππ1ππ2π 1π 2
π§ =1
πΆπ(1
ππ2β π π§)
ππ’ =ππ1
πΆπΆπππ’π‘π‘
=πΌ
πΆπΆ
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Your Name EE 536a Final Project Presentation December 3, 2014
NMOS Based Input Stage Amplifier[1]
First Stage Gain:
ππ7(ππ7//ππ41)
Second Stage Gain:
ππ43(ππ43//ππ42)
gm= 2π’πΆππ₯π
πΏπΌπ
ππ =1
ππΌπ
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Your Name EE 536a Final Project Presentation December 3, 2014
First Stage Performance
I=110uA
Gain= 30dB
πππ//πππ= 26.67K Ξ©
gm=1.2mΞ©β1
π’ππΆππ₯ = 500u
π
πΏ= 12
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Your Name EE 536a Final Project Presentation December 3, 2014
Second Stage Performance
πΌπ= 8mA,
Gain= 30dB
πππ//πππ =417.7Ξ©
πππ = 75m Ξ©β1
π’ππΆππ₯ = 15u
π
πΏ= 24580
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Your Name EE 536a Final Project Presentation December 3, 2014
Overall Performance
When Input at 800mV
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Your Name EE 536a Final Project Presentation December 3, 2014
PMOS Based Input Stage Amplifier
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Your Name EE 536a Final Project Presentation December 3, 2014
First Stage Performance
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Your Name EE 536a Final Project Presentation December 3, 2014
Second Stage Performance
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Your Name EE 536a Final Project Presentation December 3, 2014
Overall Performance
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Your Name EE 536a Final Project Presentation December 3, 2014
MUX
Vin as a select signal
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Your Name EE 536a Final Project Presentation December 3, 2014
Overall Performance
Almost the same as before
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Your Name EE 536a Final Project Presentation December 3, 2014
Band-gap Reference Motivation
Generate Vgs for NMOS
carrying tail current
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Your Name EE 536a Final Project Presentation December 3, 2014
Band-gap Reference[2]
ππΊπ π β ππΊπ π0 + [πΎπ + ππΊπ π0 β πππ» π0 β πππΉπΉ](π
π0β 1)
ππΊπ0 β ππΊπ1 = πππ‘πππ
ππππ =
ππΊπ0 + ππ 1 + ππ 3 =ππΊπ π0
+ πΎπ + ππΊπ π0 β πππ» π0 β πππΉπΉπ
π0β 1
+π 1 + π 3π 0
πππ‘πππ
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Your Name EE 536a Final Project Presentation December 3, 2014
Band-gap Reference
Name After Tuning π
πΏ M0
5
π
πΏ M1
11.5
π
πΏ M3,4
0.8
π
πΏ M5,6
8
π
πΏ M7
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π 0 30kΞ©
π 1 150kΞ©
π 2 50kΞ© π 3 100kΞ©
π 4 100kΞ©
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Your Name EE 536a Final Project Presentation December 3, 2014
Vref
Add a voltage dividor to
get desired votlage
reference
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Your Name EE 536a Final Project Presentation December 3, 2014
OTA Schematic
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Your Name EE 536a Final Project Presentation December 3, 2014
Unity-Gain Closed-Loop Small-Signal Response
π΄
1 + π΄β 1
3dB BW increase from 6KHz to 26MHz
A = 74dB = 5000
Input at 800mV
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Your Name EE 536a Final Project Presentation December 3, 2014
Unity-Gain Closed-Loop Small-Signal Transient
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Your Name EE 536a Final Project Presentation December 3, 2014
Unity-Gain Closed-Loop Large-Signal Transient
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Your Name EE 536a Final Project Presentation December 3, 2014
Open-Loop Input-Referred Voltage Noise
Corner frequency
100 Hz
Vn,in=πΎ
πΆππ₯ππΏπ=0.013
π1π
=3πππΎ
8ππππΏπΆππ₯=141.65KHz
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Your Name EE 536a Final Project Presentation December 3, 2014
CMRR
80dB at 1Hz
38dB at 10MHz
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Your Name EE 536a Final Project Presentation December 3, 2014
PSRR
67dB at 1 Hz
32 dB at 10MHz
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Your Name EE 536a Final Project Presentation December 3, 2014
Open-Loop Small-Signal Response at Corners
0.9V -20π @200mV of Input
Gain: 68dB
PM:680
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Your Name EE 536a Final Project Presentation December 3, 2014
Open-Loop Small-Signal Response at Corners
0.9V +20π @200mV of Input
Gain: 64dB
PM:760
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Your Name EE 536a Final Project Presentation December 3, 2014
0.9V 85π @200mV of Input
Gain: 61dB
PM:800
T goes up
Gain goes
down
Open-Loop Small-Signal Response at Corners
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Your Name EE 536a Final Project Presentation December 3, 2014
Open-Loop Small-Signal Response at Corners
1V -20π @200mV of Input
Gain: 74dB
PM:670
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Your Name EE 536a Final Project Presentation December 3, 2014
Open-Loop Small-Signal Response at Corners
1V 20π @200mV of Input
Gain: 66dB
PM:700
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Your Name EE 536a Final Project Presentation December 3, 2014
Open-Loop Small-Signal Response at Corners
1V 85π @200mV of Input
Gain: 64dB
PM:710
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Your Name EE 536a Final Project Presentation December 3, 2014
Open-Loop Small-Signal Response at Corners
1.1V -20π @200mV of Input
Gain: 64dB
PM:700
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Your Name EE 536a Final Project Presentation December 3, 2014
Open-Loop Small-Signal Response at Corners
1.1V 20π @200mV of Input
Gain: 61dB
PM:770
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Your Name EE 536a Final Project Presentation December 3, 2014
Open-Loop Small-Signal Response at Corners
1.1V 85π @200mV of Input
Gain: 55 dB
PM:820
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Your Name EE 536a Final Project Presentation December 3, 2014
Large-Signal Output Spectrum
Output swing:0.7V
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Your Name EE 536a Final Project Presentation December 3, 2014
Performance Summary
οΌexception for input at 400mV-500mV
Name Target Analytical Estimation Simulated Result
Avd β₯60dB 60dB οΌβ₯60dB Best:75dB
fu β₯100GHz 300MHz 20MHz
SR β₯5000V/US 62.5V/us ~13000V/s
ts β€50ps 10000ps 81.63n
Vn,in β€1nV/sqrt(Hz) 0.013 0.14nV/sqrt(Hz)
f1/f β€10KHz 141.65KHz 100Hz
THD 0.001% 0 0
CMRR β₯80dB at DC
β₯60dB at 10MHz
β₯80dB at DC
β₯60dB at 10MHz
80dB at DC
40dB at 10MHz
PSRR β₯60dB at DC
β₯40dB at 10MHz
β₯60dB at DC
β₯40dB at 10MHz
67dB at DC
32dB at 10MHz
Vdd 1V 1V 1V
Vin,rr β₯0.9V β₯0.9V β₯0.9V
Vin,CM 0.1-0.9V 0.1-0.9 0.1-0.9
Vout,rr β₯0.9V β₯0.9V 0.7V
IDC β€25mA β€25mA β€25mA
CL 100fF 100fF 100fF
PM β₯60o 60o οΌβ₯60o Best 80o
GM β₯10dB β₯10dB β₯20dB
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Your Name EE 536a Final Project Presentation December 3, 2014
Highlights of the design:
Mixed Signal Design
Improvement suggestions:
Increase current to increase the Slew Rate.
Pole cancellation to Increase unity-gain cut-off frequency
Lessons learned
Start the project early
Conclusions
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Your Name EE 536a Final Project Presentation December 3, 2014
[1] K.T. Hafeez. ββDesign of Two Stage Operational Amplifierββ, IIT.
Web:
https://www.youtube.com/channel/UCEXcqylc45jam5xa6vvEG7A
[2]H.L. Wang, X.X. Zhang, Y.J. Dai, et al. ββA Low-Voltage Low-Power
CMOS Voltage Reference Based on Subthreshold MOSFETββ Journal of
Semiconductors, Vol.32, No.8, Aug 2011
References
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