assignment electrical
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8/18/2019 Assignment Electrical
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Assignment No.:1.A
1. Consider a pMOS system with the following parameters:
tox=250Ǻ; NA=1.1015cm-3; ND=1.1020cm-3 and Nox=2.1010cm-2
a.
Determine the threshold voltage VTO for VSB=0. Use εox=3.97εo and εsi=11.7εo for the dielectric coefficients of silicon-dioxide and silicon respectively.
b. Determine the type and the amount of channel ion implantation which are
necessary to achieve a threshold voltage of 1.2V and -1.2V.
2. Calculate the threshold voltage VTO at VSB=0, for a polysilicon gate n-channel MOS
transistor, with the following parameters:
tox =450Ǻ; NA=2.1015
cm
-3
; ND=2.10
20
cm
-3
and Nox=3.10
10
cm
-2
. Calculate the substrate bias coefficient and plot the VT as a function of VSB. The voltage VSB will be assumed to
vary between zero and 6V.
3. For an n-channel MOS transistor with μn=500cm2/V.s, Cox=5.10-8F/cm2,W=18μm,
L=2μm and VTO=1V, examine the relationship between the drain current and the terminal
voltages. Also find the value of β and plot ID as a function of VDS, for VGS=3,4 and 5V.
4.
A set of I-V characteristics for a MOS transistor is shown below for different biasing
conditions. Determine the type of the device. Assume φF= -0.3V. Plot the square root of
the drain current as a function of VGS. From the graph, find VT for VSB=0V and 3V. Also
find the value of substrate bias coefficient. Neglect the channel length modulation effect.
VGS(V) VDS(V) VSB(V) ID(μA)
2.5 2.5 0.0 49
4 4 0.0 235
5 5 0.0 433
2.5 2.5 3.0 23
4 4 3.0 173
5 5 3.0 347
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5. A MOS transistor has the following device parameters:
μn=500cm2/V.s; tox=500Ǻ; W=20μm;L=0.6μm
What is the operating region at the bias conditions shown in table and find the drain to
source current?
Fig. (a) Fig. (b)
Fig. (c) Fig. (d)
Fig. No. VD(V) VG(V) VS(V) Mode of operation IDS(A)
a 7 5 0 ? ?
a 2 1 2 ? ?
a -2 6 1 ? ?
a 9 2 -5 ? ?
b 5 -5 -2 ? ?
b -4 1 0 ? ?
b -5 -3 4 ? ?
b -5 5 8 ? ?
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