EE 434 Lecture 23

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EE 434Lecture 23

• Models for Computer Simulation
• Bipolar Small Signal Device Models

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Quiz 15
The collector current IC was accurately measured
to be 1.5mA and the VBE was measured to be 0.65V.
What is the JS for the process if the emitter
area is 100u2? Assume operation at room
temperature.
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And the number is .
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And the number is .
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Quiz 15
The collector current IC was accurately measured
to be 1.5mA and the VBE was measured to be 0.65V.
What is the JS for the process if the emitter
area is 100u2? Assume operation at room
temperature.
Solution
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Simple dc model
Review from Last Time
Typical Output Characteristics
Saturation
IC
Forward Active
VBE or IB
VCE
Cutoff
Forward Active region of BJT is analogous to
Saturation region of MOSFET
Saturation region of BJT is analogous to Triode
region of MOSFET
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Improved dc model
Review from Last Time
IC
VBE or IB
VCE
Valid in All regions of operation
VAF effects can be added
Not mathematically easy to work with
Note dependent variables changes
Termed Ebers-Moll model
Reduces to previous model in FA region
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Simple dc model
Review from Last Time
Simplified Multi-Region Model
VBEgt0.4V VBClt0
Forward Active
VBE0.7V VCE0.2V
ICltßIB
Saturation
VBElt0 VBClt0
ICIB0
Cutoff
A small portion of the operating region is missed
with this model but seldom operate in the missing
region
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Simple dc model
Review from Last Time
Equivalent Simplified Multi-Region Model
VBEgt0.4V VBClt0
Forward Active
VBE0.7V VCE0.2V
ICltßIB
Saturation
VBElt0 VBClt0
ICIB0
Cutoff
A small portion of the operating region is missed
with this model but seldom operate in the missing
region
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Models for Computer Simulation
Simple dc Model
Small Signal Model
Better Analytical dc Models
Sophisticated Model for Computer Simulations
Frequency-Dependent Small Signal Model
Better Models for Predicting Device Operation
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Models for Computer Simulation
MOS Transistor
Model Parameters
Physical Parameters
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Models for Computer Simulation
MOS Transistor
Resistance May Exist in the Drain and Source
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Models for Computer Simulation
MOS Transistor
Resistance May Exist in the Drain and Source
Where is the drain and the source D and S?
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Models for Computer Simulation
MOS Transistor
Where is the drain and the source D and S?
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Models for Computer Simulation
MOS Transistor
Where is the drain and the source D and S?
Considerable Interconnect may be made with
diffusions
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Models for Computer Simulation
MOS Transistor
Where is the drain and the source D and S?
Considerable Interconnect may be made with
diffusions
Drain and source boundary assignments is not
unique !!
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Models for Computer Simulation
MOS Transistor
Where is the drain and the source D and S?
Drain and source boundary assignments is not
unique !!
So, how are boundary assignments made?
However you want !!
But eventually must either include all parasitics
as either part of devices or as parts of
interconnects
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Models for Computer Simulation
MOS Transistor
Model Parameters
Physical Parameters
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Models for Computer Simulation
MOS Transistor Models for SImulation
Physical Parameters

• Separate Process Part of Model from
  Instantiation part of Model
• Use one Process File for Entire Process and
  Specify only Physical
• Geometric Parameters for Each Device

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Models for Computer Simulation
MOS Transistor Models for SImulation
Physical Parameters
MOS Models for Simulation Level 1 Level
2 Level 3 BSIM 3 BSIM 4 PSP
Hierarchy Used in Models
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