ed exp 12
DESCRIPTION
LAB ELECTRONICSTRANSCRIPT
Laboratory Exercises for Electronic Devices, Buchla, © 2001 Prentice-Hall, Inc.
Experiment 12Troubleshooting Problem
?
Assume resistor R1 is shorted so that the gate power supply is connected directly to the JFET in Figure 12-2. What effect would this have on the measured quantities in this experiment?
10 k
100
2N 5458
D
S
G
+
+R 1
V G G
V D D
R 2
Laboratory Exercises for Electronic Devices, Buchla, © 2001 Prentice-Hall, Inc.
Experiment 12Troubleshooting Problem Solution
Assume resistor R1 is shorted so that the gate power supply is connected directly to the JFET in Figure 12-2. What effect would this have on the measured quantities in this experiment?
10 k
100
2N 5458
D
S
G
+
+R 1
V G G
V D D
R 2 None whatsoever.
So why was it placed in the circuit? The answer is to protect the FET in case the gate power supply is accidentally reversed.
Laboratory Exercises for Electronic Devices, Buchla, © 2001 Prentice-Hall, Inc.
Experiment 12Related Problem-1
Assume the JFET in Figure 12-2 is connected with the drain and source reversed. What effect would this have on the drain current as compared to the correct connection?
10 k
100
2N 5458
D
S
G
+
+R 1
V G G
V D D
R 2 a) Drain current would be about the same.
b) There will be much less drain current.
c) The will be no drain current.
Laboratory Exercises for Electronic Devices, Buchla, © 2001 Prentice-Hall, Inc.
Experiment 12Related Problem-1 Solution
10 k
100
2N 5458
D
S
G
+
+R 1
V G G
V D D
R 2
Assume the JFET in Figure 12-2 is connected with the drain and source reversed. What effect would this have on the DC drain current as compared to the correct connection?
a) Drain current would be about the same.
b) There will be much less drain current.
c) The will be no drain current.
The source and drain are connected to opposite ends of the channel. Reversing their connection has little effect on the DC drain current (but is not a good idea because of capacitance and other effects).
Laboratory Exercises for Electronic Devices, Buchla, © 2001 Prentice-Hall, Inc.
Experiment 12Related Problem-2
10 k
100
2N 5458
D
S
G
+
+R 1
V G G
V D D
R 2
Can the gate and source connections also be reversed with little effect?
a) Yes they can.
b) Absolutely not!
Laboratory Exercises for Electronic Devices, Buchla, © 2001 Prentice-Hall, Inc.
Experiment 12Related Problem-2 Solution
10 k
100
2N 5458
D
S
G
+
+R 1
V G G
V D D
R 2
Can the gate and source connections also be reversed with little effect?
a) Yes they can.
b) Absolutely not!
Reversing the gate and source will forward bias the gate source junction. Drain current may be too high and the input resistance will be significantly less.