Transcript Slide 1

5.2a Poly Resistor
• Value of resistor is from Problem 5.1=1KΩ
• Sheet resistance of poly=25Ω/
• Thus number of squares in poly
resistor=1KΩ/25Ω/
=40
• Therefore L/W=40.
• Minimum feature size (2l)=2mm
• Thus if we assume width of poly resistor to be
2mm then length of the resistor is 80mm.
1
Steps in Layout of
Resistor
• Since the minimum dimension in question 5.2 is
2mm. Therefore we should use the technology
file corresponding to l=1mm
2
Resistor Layout
There are 5 long
sections of length 17l
and width 2l
Thus the number of
squares is
(5x17)/2~42
Also the edges
contribute another 4
squares
There is additional
resistance due to
current crowding at the
corners and also the
poly contact regions add
additional resistance.
3
• W/L of nfet was 90
• Since L is 2l=2mm, W=180mm (90x2l)
• Remember to account for Ld (lateral diffusion) in
L of NMOS
4
Extraction
• Once layout is drawn,
DRC cleared and saved,
it is ready to be extracted
• Go to tools and click on
extract
• The window shown will
appear. In the definition
file tab, choose the
appropriate technology
file from the folder it is
present by browsing.
• Then hit run, the
extracted output file can
be opened with notepad.
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Extracted file
The extracted file will look as such
This is the information
required from extracted file to
be used in spice
Note: L=2.5mm to account for
lateral diffusion mentioned in
q.5.2
6
Pspice
•
First draw the circuit.
Choose MbreakN part and place
it.
– Goto edit and click on model
– Choose the Edit instance model
(text)
– Add the model parameters as
below and click ok
.model NMOD NMOS (
LEVEL=1,
VTO=1
GAMMA=0.2
KP=20U)
*$
– Also double click on part and
change the attributes according to
extracted Ledit file
– Other parameters and other level
models can also be added for
more complex simulations
•
Finish the circuit by adding the dc
source
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Analysis
• Choose dc sweep
analysis
• Click on the this tab
and choose the
voltage source to be
swept and its range
• Here the input voltage
name is V3 and it was
initialized to 0V
8
DC Sweep response
9
VIL,VIH
determination
The blue curve represents dVout/dVin, the markers point to where
the slope is -1
VIL=1.5V, VIH=3.09V
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