In this experiment, we will be studying the properties of metal oxide semiconductor field effective transistors (MOSFETs). MOSFETs are categorized into PMOS and NMOS, corresponding to p-type substrate channels and n-type substrate channels. We will study DC input and output characteristics for both PMOS and NMOS. We will also build a CMOS logic amplifier and measure its DC and AC characteristics, including gain and transconductance values.
Part 1
A) DC Input Characteristics for PMOS
Vsg
Vdd
P
R1
1k
R
D
= 1005(Ω)
PMOS Circuit 1
Build circuit 1 as shown above. Adjust the bias voltages such that V
SD
stays constant at
5V. Start at V
GS
= 0 and increase it to measure V
RD
to get the current through the PMOS.
Table 1. DC Input Characteristics for PMOS
V
DS
(V) V
GS
(V)
5
5
5
5
5
5
5
5
5
-0.342
-0.712
-1.159
-1.204
-1.312
-1.4
-1.517
-1.703
5
5
5
5
5
5
-1.949
-2.208
-2.54
-2.833
-3.555
-4.237
V
RD
(V)
-0.002
-0.011
-0.025
-0.058
-0.136
0
0
0
0
-0.29
-0.505
-0.857
-1.225
-2.345
-3.626
I
D
(A)
-1.99005E-06
-1.09453E-05
-2.48756E-05
-5.77114E-05
-0.000135323
0
0
0
0
-0.000288557
-0.000502488
-0.000852736
-0.001218905
-0.002333333
-0.00360796

-5 -4 -3 -2 -1
0,0005
0
-0,0005
-0,001
-0,0015
-0,002
-0,0025
-0,003
-0,0035
0
-0,004
Id (A)
We graph the current through the PMOS as a function of V
GS
at a constant V
DS
= 5v. The graph shows there is no drain current when VGS is below a threshold voltage and increases rapidly after it is larger than the threshold voltage.
B) DC Output Characteristics for PMOS
Continue with circuit 1. Bias the circuit such that V
SD
= 5V, and V
RD
= 1V. Then measure the V
SG and keep it constant. Now, vary V
DD
, and measure the corresponding V
SD
, V
RD
and calculate the current. Then repeat the process for V
RD
= 2V and V
RD
= 4V.
Table 2. (V
RD
= 1V)
V
GS1
(V)
-2.674
-2.674
-2.674
-2.674
-2.674
-2.674
-2.674
-2.674
-2.674
-2.674
-2.674
-2.674
-2.674
V
D
(V)
0
-0.273
-0.618
-0.88
-0.983
-1.012
-1.036
-1.04
-1.079
-1.109
-1.135
-1.157
-1.185
I
D
(mA)
0
-0.0002716
-0.0006149
-0.0008756
-0.0009781
-0.001007
-0.0010308
-0.0010348
-0.0010736
-0.0011035
-0.0011294
-0.0011512
-0.0011791
V
DS
(V)
0
-0.065
-0.244
-1.728
-2.68
-3.71
-4.78
-5.05
-5.94
-7.17
-8.11
-8.97
-11.34
Table 3. (V
RD
= 2V)
V
GS2
(V) V
-3.27
D
(V)
0.002
-3.27
-3.27
-0.187
-0.319
I
D
(mA)
1.99005E-06
-0.00018607
-0.00031741
V
DS
(V)
-0.002
-0.115
-0.199

-3.27
-3.27
-3.27
-3.27
-3.27
-3.27
-3.27
-3.27
-3.27
-3.27
-3.27
-0.525
-0.757
-0.923
-1.134
-1.307
-1.495
-1.614
-1.8
-2.007
-2.221
-2.495
-0.00052239
-0.00075323
-0.00091841
-0.00112836
-0.0013005
-0.00148756
-0.00160597
-0.00179104
-0.00199701
-0.00220995
-0.00248259
-0.343
-0.517
-0.674
-0.885
-1.094
-1.405
-1.712
-3.093
-6.95
-14.97
-24.45
V
GS3
(V)
-4.12
-4.12
-4.12
-4.12
-4.12
-4.12
-4.12
-4.12
-4.12
-4.12
-4.12
-4.12
V
D
(V)
0.002
-0.114
-0.509
-0.91
-1.505
-2.007
-2.519
-3.03
-3.197
-4.03
-4.673
-4.961
Table 4. (V
RD
= 4V)
I
D
(mA)
V
DS
(V)
1.99E-06 0.001
-0.0001134 -0.002
-0.0005065 -0.008
-0.0009055 -0.021
-0.0014975 -0.105
-0.001997 -0.53
-0.0025065 -0.917
-0.0030149 -1.387
-0.0031811 -1.56
-0.00401 -3.36
-0.0046498 -10.74
-0.0049363 -14.97
0,001
-30 -25 -20 -15 -10
0
-5
-0,001
0
-0,002
-0,003
-0,004
-0,005
5
Vrd = 1v
Vrd = 2v
Vrd = 4v
-0,006
Vds (V)
In this section, we observe the current through the PMAS which has a constant voltage across the input at V
GS
and varying V
DS
. We see that larger V
RD corresponds to larger V
GS3 and larger I
D.

C) AC Transconductance for PMOS
Continuing with the same circuit, we will measure the AC characteristics of the PMOS transistor. Adjust the bias voltages (V
GS
) such that the following conditions are met.
Large signal: V
SD
= 5.00V I
D
= 0.5mA V
DD
= 5.5V
Small signal: v
SG
= 200mV P-P, 10kHz
And then measure the V
RD to find I
D
gm = Id/V
GS
Table 5 v gs
(V)
0.2 v
RD
(V) i d
(A) g m
(1/ohm)
0.16 0.0001592 0.00079602
Part 2
A) DC Input Characteristics for NMOS
RD 1k
N
Vgs Vdd
NMOS Circuit 2
Build and Bias circuit 2 as shown above, setting VDS at a constant of 5V. Similarly to the
PMOS, varying VGS and measure change in current.
Table 6
V
DS
(V)
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
V
GS
(V)
0.011
0.139
0.204
0.506
0.774
0.993
1.051
1.157
1.204
1.666
1.828
2.186
2.469
2.714
3.007
3.3
3.818
4.199
5.062
V
RD
(V) I
D
(A)
0.001 9.95025E-07
0.001 9.95025E-07
0.001 9.95025E-07
0.001 9.95025E-07
0.001 9.95025E-07
0.001 9.95025E-07
0.001 9.95025E-07
0.001 9.95025E-07
0.001 9.95025E-07
0.002 1.99005E-06
0.01 9.95025E-06
0.092 9.15423E-05
0.245 0.000243781
0.442 0.000439801
0.755 0.000751244
1.176 0.001170149
2.017 0.002006965
2.83 0.00281592
5.023 0.00499801

0,006
0,005
0,004
0,003
0,002
0,001
0
0 1 2 3
Vgs (V)
4 5 6
Graph 3 shows the DC input characteristics of the NMOS transistor. The graph shows the drain current behavior as its gate to source voltage is changed while its drain to source voltage is kept constant just like the PMOS. Notice the in the NMOS, the gate voltage is higher than the source voltage, whereas in the PMOS, the source voltage is higher than the gate voltage.
B) DC Output Characteristics for NMOS
Keep the same circuit in part a for the NMOS, and adjust the bias voltages such that
V
DS
= 5V, and V
RD
= 1V. Then, measure V
GS
and keep it constant. Vary V
DD
, and measure the corresponding V
DS
, V
RD
and calculate the current. Repeat by with V
RD
= 2V and V
RD
=
4V.
V
GS1
(V)
3.266
3.266
3.266
3.266
3.266
3.266
3.266
3.266
3.266
3.266
3.266
3.266
3.266
3.266
3.266
Table 6 ( V
RD
=1v)
V
RD
(V) I
D
(mA)
0.019 1.89055E-05
0.114 0.000113433
0.362 0.000360199
0.639 0.000635821
1.014 0.001008955
1.124 0.001118408
0.795 0.000791045
0.206 0.000204975
0.508 0.000505473
0.907 0.000902488
1.308 0.001301493
1.07 0.001064677
1.091 0.001085572
1.102 0.001096517
1.117 0.001111443
V
DS
(V)
0.007
0.043
0.147
0.292
0.673
6.54
0.398
0.08
0.218
0.499
13.52
1
1.976
3.052
5.017

V
GS2
(V)
3.824
3.824
3.824
3.824
3.824
3.824
3.824
3.824
3.824
3.824
3.824
3.824
3.824
Table 7 ( V
RD
=2v)
V
RD
(V) I
D
(mA)
0 0
0.557 0.000554229
0.939 0.000934328
1.359 0.001352239
1.661 0.001652736
1.768 0.001759204
1.884 0.001874627
1.948 0.001938308
2.052 0.002041791
1.983 0.001973134
2.01 0.002
2.026 0.00201592
2.184 0.002173134
V
DS
(V)
0
0.17
0.308
0.501
0.699
0.805
1.009
1.494
8.79
3.034
4.998
6.578
12.3
V
GS3
(V)
4.695
4.695
4.695
4.695
4.695
4.695
4.695
4.695
4.695
4.695
4.695
4.695
4.695
4.695
4.695
Table 8 ( V
RD
=4v)
V
RD
(V) I
D
(mA)
0.003 2.9851E-06
-0.53 -0.0005274
-0.901 -0.0008965
-1.622 -0.0016139
-2.615
-3.024
-0.002602
-0.003009
-3.438 -0.0034209
-3.784 -0.0037652
-3.876 -0.0038567
-3.905 -0.0038856
-3.934 -0.0039144
-3.948 -0.0039284
-3.954 -0.0039343
-3.973 -0.0039532
-4.014 -0.003994
V
DS
(V)
0.001
-0.113
-0.138
-0.272
-0.575
-0.864
-1.107
-1.519
-2.021
-2.56
-3.526
-4.134
-5.048
-6.225
-7.29
-5
0,005
0,004
0,003
0,002
0,001
0
-0,001
0
5
Vds (V)
10 15
Vrd = 1v
Vrd = 2v
Vrd = 4v

The graph and table show the output characteristics for NMOS transistor. V
GS
is kept constant voltage and V
DS
is changed to find how the drain current varies with different output voltage.
C) AC Transconductance for NMOS v gs
(V)
0.2 v
RD
(V)
0.2 i d
(A)
0.000199 g m
(1/ohm)
0.00099502
Part 3 CMOS Amplifier
P,
M2
R
Vdd
+
100k
C N,
M1 ch2
+
-50mV/50mV
10kHz ch1
100uF
0.5mA
-
-
R= 101.1k Ω, C = 100uF
Circuit 3
First, we measure the DC values. And then, we apply a 10kHz sine-wave to the input, such that V in,pp
= 200mV P-P. Measure V out,pp and calculate the gain.
We measure v in
For M2, V
GS
= V
= 200mV p-p,
DS1
→ v
DS
≧ V
DS v
- out
V
= 208mV p-p, V
DS1
TH
= 2.844V, V
DS2
, in saturation region.
= -3.228V
For M1, I
A
V
= 𝑣 𝑜𝑢𝑡 𝑣 𝑖𝑛
=
G
= 0→
212 mV
200mV v
DS
= V
GS
= 1.06
, in saturation region.
In this experiment, We examined the AC and DC characteristics of both PMOS and NMOS. In DC input characteristic parts, the threshold voltages measured were close to our expectations. For
AC parts, we calculated transconductances from the two transistors separately and verify their ratio with the gain of the CMOS amplifier. However, there may be a large error in our results because the AC measurements fluctuated greatly.