Amplifier Layout
description
Transcript of Amplifier Layout
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KLE Societys B.V. Bhoomaraddi College of Engineering and Technology,
Hubli
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A LAYOUT DESIGN OF SINGLE ENDED DIFFERENTIAL AMPLIFIER
Under the guidance of Dr. R B Shettar
Mentor : Mr. Charan
By, Mr. Abhishek C Math
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Overview
Objective
What is Layout??.
Types of Layout
Matching of Device
Layout Design Techniques
Specification
Diff pair layout
Results
concluison
References
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Objective
Design the layout of Single ended Differential
Amplifier and verify the post layout simulation with the Schematic
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Analog Layout Design
What is Layout??...
The process of creating an accurate physical representation of an engineering drawing (netlist) that conforms to constraints imposed by the manufacturing process, the design flow and the performance requirements shown to be feasible by simulation.
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Full Custom IC Design Flow
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Types of Layout :
1.Building Block Layout
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2.Interconnection Layout
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3. Floorplanning layout
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MATCHING OF A DEVICE
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MATCHING
Two devices with the same physical layout never have quite the same electrical properties.
Variations between devices are called mismatches
A large variety of analog circuits rely on Matching of transistors. Circuits like differential pair rely on gate to source voltage matching while current mirrors rely on current matching.
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REASONS FOR MISMATCH
Mismatches may be either random or systematic, or a combination of both.
Suppose two matched devices have parameters P1 and P2.
Then let the mismatch between the devices equal P = P2 P1.
For a sample of units, measure P . Compute sample mean m(P ) and standard
deviation s(P ).
m(P ) is a measure of systematic mismatch. s(P) is a measure of random mismatch.
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RANDOM MISMATCH
Random mismatches due to microscopic fluctuations in dimensions, doping, oxide thickness and other
parameters that influence component values.
Random mismatches cannot be eliminated, but they can be reduced by increasing device dimensions
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SYSTEMATIC MISMATCH
Systematic mismatches which are caused by :
Process biases
Mechanical stress
Temperature gradients
Polysilicon etch rates etc
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Systematic mismatches may also arise from gradients.
Certain physical parameters may vary gradually across an integrated circuit, for example:
Temperature
Pressure
Oxide thickness
Because of the way we mathematically treat these variations, they are called gradients.
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Rules for MOS transistor matching
Place transistors in close proximity. Orient transistors in the same direction. Keep the layout of the transistors as compact as
possible Whenever possible use Common centroid layouts. Place transistors segments in the areas of low stress
gradients. Place transistors well away from the power devices. For current matching keep overdrive voltage large. For voltage matching keep overdrive voltage
smaller.
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Layout Design Techniques
1. Interdigitization
Process gradient almost evenly distributed between components A and B . A and B are split into units
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Common Centroid
Perfect cancelation of linear gradients. Several patterns are possible. Can split A and B into
more than two units.
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SPECIFICATION
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SCHEMATIC
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PRE SIMULATION
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LAYOUT OF DIFF PAIR
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RC EXTRACTION
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POST SIMULATION
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Result
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SPECIFICATION PRE SIMULATION POST SIMULATION
DC GAIN(dB) 51.92 51.9
UGB(MHz) 10.54 10.38
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Conclusion
The layout of single ended differential amplifier is designed in cadence UMC 180nm technology virtuoso.
Pre and post simulation is verified.
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References
Seong K. Hong and Phillip E. Allen [21a. 'ANALOG CIRCUIT LAYOUT WIT'H OPTIMIZED PERFORMANCE"
Alan Hastings." The Art of Analog Layout (Sencond Edition), 2007."
Behzad Razavi, . "Design of Analog CMOS Integreated Circuits, 2001."
Dan Clein."CMOS IC LAYOUT Concepts, Methodologies, and Tools
Pelgrom, M. J. M., Duinmaiger, A. C. J., and Welbers, A. P. G., Matching Properties of MOS Transistors, IEEE J. Solid-State Circuits, Vol. SC-24, Oct. 1989, pp. 1433-1439
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THANK YOU
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