MAEZLIN J AVILA-TAYLOR, ID 112003784
Friday, January 30, Spring 2004
2.3 Lay out (using a path object in LASI or any other layout program) a nominally
250kilo-ohm resistor using the n-well and the serpentine pattern shown in Fig. 2.28.
Assume that the maximum length of a segment is 100 and the sheet resistance is 2kiloohm/square. Design rule check the finished resistor. If the scale factor in the layout is
50nm, estimate the fabricated size of the resistor.
L=250K*6/2K=750
Setting the Width of the path equal to 6 (the min)
Setting all segments to a max of 100 means two horizontal segments will be equal to 100;
the other two horizontal segments will be equal to 97, leaving 750-2*100-2*97= 366 to
be drawn. Since each corner has only 60% of sheet resistance and there are 6 corners,
the total length in corners is 0.6*6*6=21.6 leaving 366-21.6=344.4 to be drawn with
vertical segments. There are only 3 vertical segments if we wish to draw a pattern like
the one in Fig 2.28. It is impossible to draw 344.4 in length with only 3 segments of max
100. About 44.4 length would be left out of drawing. This results in a loss of 14.8
Kohms. The following figure shows the resulting 235.2Kohm resistor lay out in LASI:
235.2Kohm Resistor with FIGURE 2.28 exact pattern
This design passed the DRC check.
In order to draw a 250Kohm resistor with a max lenght of a segment 100, the serpentine
pattern would have to have more than 3 vertical segments, or we would have to set the
width to less than 6 which would not pass the DRC check.
The pattern above would result in the 250K. It also passes the DRC check. The width is
still 6 which would result in 50nm*6= 300nm. The horizontal length of each segment is
100*50nm=5micro-meters. The total vertical length is 162.5*50nm= 8.1micro-meters
Justin Wood
EE 4/510
Problem 2.7
2.7)
Using the diode of Example 2.3 in the circuit of Figure 2.29, estimate the
frequency of the input signal when the AC component of Vout is 707µV (i.e.
estimate the 3dB frequency of the Vout/Vin).
Figure 2.29
From Example 2.3
Cj =
1.120 pF
0.33
 V 
(1 −  D 
 0.759 
V D = −VOUT ≈ −1V − 0.000707V = −1.000707V
∴C j =
1.120 pF
 − 1.000707 
(1 − 

 0.759 
0.33
= 848 fF
The transfer function is determined by using the voltage divider as shown below.
1




jωC 

Vout = Vin
1 
 R +

jωC 

1




Vout  jωC  jωC 
1

 =
=

1  jωC  jωCR + 1
Vin
 R +

jωC 

1




jω C 

Vout = Vin

1 
R+

jωC 

1




1
Vout  jωC  jωC 

 =
=


1  jωC  jωCR + 1
Vin
R+

jω C 

Substituting :
Vout = 0.000707
Vin = 0.001
0.000707
1
=
0.001
jωCR + 1
0.707 =
1
jωCR + 1
ωCR = 1
ω=
f =
1
1
=
= 117924528rad / s
CR 848e − 15 *10000
ω
= 18768271Hz
2π
or
− 3dB =
1
Vout
=
Vin
jωCR + 1
− 3dB = 20 log10 =
0.707 =
1
jωCR + 1
1
jωCR + 1
ωCR = 1
ω=
f =
1
1
=
= 117924528rad / s
CR 848e − 15 *10000
ω
= 18768271Hz
2π
By Vehid Suljic
Problem 2.10
Estimate the delay through a 1 MEG resistor (10 by 2000) using the values given in Ex.
2.5. Verify the estimate with SPICE.
From Ex. 2.5 we have that (10 x 10) square’s parameters are:
C = 5 fF and R = 5 kΩ and l = 2000/10 = 200
Now we can estimate the delay through the resistor,
td = 0.35 o R o C o (l ^ 2) ≅ 350n sec
Figure 1 shows WinSpice plot of Vin and Vout vs. time. From the plot we can see that
our delay (Vout is at 50% of Vin = 500mV) is about 400 nsec which is close to what we
calculated above.
Figure 1. Spice simulation results for problem 2.10
*** Problem 2.10 top level netlist***
.control
destroy all
run
plot vin vout
.endc
.tran 1n 2u
O1
Vin 0
Rload Vout 0
Vin vin
0
Vout 0
1G
DC
0
.model TRC
R=5k C=5f len=200
.end
ltra
TRC
pulse 0 1 20n 0
KRISHNAMRAJU KURRA
HW#3
DATE: 02/02/04
2.14: Estimate the storage time, that is ,the time it takes to remove the stored charge ina
diode, when TT = 5 ns, VF = 5V, VR= -5V , Cjo = 0.5 pF and R = 1K. Verify the estimate
using SPICE.
Given:
TT = 5ns
VF= 5V
VR = -5V
Cjo= .5pF
R=1k
We have:
ts = TT .ln[ (iF-iR)/(-iF)]
Where
iF=VF/R
and
iR=VR/R
Under forward bias the voltage drop across the diode = 0.7V
iF = (5 - 0.7)/1K = 4.3 mA
When the diode is reversed biased,
iR= (-5-0.7)/1K = -5.7 mA
ts = 5 ns . ln[ (4.3 + 5.7)/ 5.7] = 2.81 ns
Therefore ts = 2.81 ns
Verification using Winspice:
**8 krishnam- HW#3 Prob:2.14***
.control
destroy all
run
let id= -i(vin)*1k
plot vd vin id
.endc
.tran 100p 25n
D1
R1
Vin
vd
Vin
vin
0
vd
0
dtrr
1k
Dc
0
pulse 5 -5 10n .1n .1n 20n 40n
.Model Dtrr D tt=5E-9 cjo=5E-13
.end
Plot showing Vin, Vd, id: