Lab 6
Metal-Oxide Semiconductor
Field Effect Transistor
(MOSFET) Characterization
Objectives
To study the MOSFET characteristics and to
learn how to determine the following MOSFET
parameters:
Threshold voltage, VT
Transconductance parameter, kn
Output resistance, ro
Channel-length modulation parameter, λ
2
Equipment and Materials
NI ELVIS II+ Board
Computer Workstation with LabVIEW
software
2N7000 MOSFET
Few resistors (82Ω, 1MΩ)
3
AO1
VDD
AO0 = Analog Output 0 (VGS)
ID AO1 = Analog Output 1 (VDD)
82 W
AI0+ = Analog Input (VDS)
VDS
D D - Drain
AO0
S - Source
1 MW G AI0+
VGS 2N7000 G - Gate
Gnd AI0-
S
2N7000 Pins
Connection diagram for MOSFET Characteristics
measurement
4
Acquiring the
Characteristic Curves from
+
NI-ELVIS II Board
through LabVIEW
5
MOSFET equation operating in the
saturation region
𝟏 𝟐
𝒊𝑫 = 𝒌𝒏 𝒗𝑮𝑺 − 𝑽𝒕𝑵 𝟏 + 𝝀𝒗𝑫𝑺
𝟐
The main parameters that characterize a MOSFET
are:
Threshold voltage, Vt (VtN for nMOS)
Transconductance parameter, kn
The channel-length modulation parameter, λ
Output resistance, r0
6
Characteristic curve
A graph showing the relation existing between current vs. voltage
Input Characteristic
Curve
7
Input characteristic curve
A graph showing the relation existing between the output
current (iD) vs input voltage (vGS).
𝟏 𝟐
𝒊𝑫 = 𝒌𝒏 𝒗𝑮𝑺 − 𝑽𝒕𝑵 𝟏 + 𝝀𝒗𝑫𝑺
𝟐
ID
8
Start
Flowchart for Input VGS_Start
Plotting the input Input VGS_Stop
VGS (V) ID (mA)
characteristic Input Resolution 1
Input VDD
1.01
curve iD vs vGS 1.02
i=1
:
:
N = (VGS_Stop – VGS_Start) / Resolution
:
2.49 ID
No
Record is i <= N ? 2.55
ID
VGS Yes
i=i+1 VGS = VGS_Start + i * Resolution
Plot
ID
ID = (VDD – VDS) / 100 AO0 = VGS VGS
AO1 = VDD
AI0 = VDS End
9
Delay
LabVIEW Block Diagram for the iD vs vGS Characteristic Curve
Front Panel for the iD vs vGS Characteristic Curve in LabVIEW 1
LabVIEW Measurement File
Format to Plot the Input
Characteristic curve
VGS (V) ID (mA)
1
1.01
1.02 ID
:
:
:
2.49
2.55 12
Output Characteristic
Curve
13
Output characteristic curve
A graph showing the relation existing between the output
current (iD) vs output voltage (vDS) at constant vGS
𝟏 𝟐
𝒊𝑫 = 𝒌𝒏 𝒗𝑮𝑺 − 𝑽𝒕𝑵 𝟏 + 𝝀𝒗𝑫𝑺
𝟐
ID
14
iD vs vDS at
various values of
vGS
VGS1=2.10 VGS2=2.20 VGS3=2.30 VGS4=2.4
VDD
ID VDS ID VDS ID VDS ID VDS
0
0.1
0.2
ID
:
9.9
10.0
15
VGS1=2.10 VGS2=2.20 VGS3=2.30 VGS4=2.4
START
VDD
ID VDS ID VDS ID VDS ID VDS
Flowchart for
Input VGS_Start
Input VGS_Stop 0
0.1
Plotting iD vs
Input VGS_increment
Input VDD
0.2
:
N1 =
VGS_Stop – VGS_Start
VGS_increment
+1
vDS :
VDD
N2 =
0.1
+1
9.9
i1 = 0
AO1 10.
VDD 0
is
No
i1 < N1
?
AO0 = Analog Output 0 (VGS)
Plot Yes
ID
VDS VGS[i1] = VGS_Start + i1*VGS_increment
ID 82 W AO1 = Analog Output 1 (VDD)
END
Display VGS AI0+ = Analog Input (VDS)
i1 = i1 + 1
i2 = 0
VDS
D D - Drain
i2 = i2 + 1 is
No
AO0
i2 < N2
?
S - Source
Record Yes
1 MW G AI0+
VGS[i1]
ID[i2] VDD_Out[i2] = i2*0.1 VGS 2N7000 G - Gate
VDS[i2]
ID[i2] = (VDD_Out[i2] – VDS[i2])/100
Display VDD_Out[i2]
Gnd AI0-
S
AO0 = VGS[i1]
VDS[i2] = AI0
Delay 50 ms
AO1 =VDD_Out[i2] 2N7000 Pins
16
LabVIEW Block Diagram for the iD vs vDS Characteristic Curve
17
Front Panel for the iD vs vDS Characteristic Curve in LabVIEW 18
LabVIEW Measurement File
Format to Plot the Output
Characteristic curve
VGS1=2.10 VGS2=2.20 VGS3=2.30 VGS4=2.4
VDD
ID VDS ID VDS ID VDS ID VDS
0
0.1
0.2
ID
:
:
9.9
10.0
19
Thank you.
20
