Post on 16-Jun-2018
1 © CMOS Digital Integrated Circuits – 3rd Edition
CMOS Digital Integrated Circuits
Chapter 5 MOS Inverters:Static Characteristics
S.M. Kang and Y. Leblebici
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2 © CMOS Digital Integrated Circuits – 3rd Edition
Ideal Inverter
Voltage Transfer Characteristic (VTC) of the ideal inverter
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Generic Inverter VTC
Voltage Transfer Characteristic (VTC) of a typical inverter
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Noise Margins
Propagation of digital signals under the influence of noise
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Noise Margins
Definition of noise margins
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Noise Margins
Nominal output
Output under noise
The nominal operating region is defined as the region where the gain is less than unity !
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CMOS Inverter Circuit
8 © CMOS Digital Integrated Circuits – 3rd Edition
CMOS Inverter Circuit
9 © CMOS Digital Integrated Circuits – 3rd Edition
CMOS Inverter Circuit
inversion (switching) threshold voltage
determine noise
margins
10 © CMOS Digital Integrated Circuits – 3rd Edition
CMOS Inverter Circuit
nMOS transistor current-voltage characteristics
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CMOS Inverter Circuit
pMOS transistor current-voltage characteristics
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CMOS Inverter Circuit
Intersection of current-voltage surfaces of nMOS and pMOS transistors
13 © CMOS Digital Integrated Circuits – 3rd Edition
CMOS Inverter Circuit
Intersection of current-voltage surfaces gives the VTC in the voltage plane
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CMOS Inverter Circuit
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CMOS Inverter Circuit
How to choose the kR ratio to achieve a desired inversion threshold voltage:
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CMOS Inverter Circuit
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Supply Voltage Scaling
VTC of a CMOS inverter for different power supply voltage values.
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VTC of a CMOS inverter, when operated with a supply voltage that is smaller than (VTn + VTp ).
Hysteresis behavior !
Supply Voltage Scaling
19 © CMOS Digital Integrated Circuits – 3rd Edition
CMOS Inverter Layout
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CMOS Inverter Layout
Mask layoutof the inverter
Simplifiedcross-section