Applications
3-6
2000) by base current (sourced by the Model 224). A profile
of the transistor operating characteristics can be obtained by
measuring the collector current over a specified voltage
range (V) for different base bias currents. For example, Fig-
ure 3-6 shows the characteristics of a typical NPN silicon
transistor at base bias currents (I) of 20µA, 40µA, 60µA and
80µA.
Figure 3-5
Transistor current gain checks
2 0 0 0 M U L T I M E T E R
Volts HI
Volts LO
1
2
3
4
H
H
A
B
Model 7077
H
H
E
F
H
H
C
D
H
G H
G H
G H
G
L
L
L
L
L
L
H
G
L
H
H
L
AAA
AAA
AAA
Model 224
Model 2000
AAA
AAA
AAA
Model 230
Measure
V or I
Source
V
Source
I
Amps HI
Amps LO
Output
Common
HI
LO
A
±
224
2000
230
I
B
I
C
I
E
V
CE
I
C
I
B
Gain =
Equivalent Circuit
3.3.1 Current gain checks
The dc current gain of a general purpose transistor can be
checked by configuring the transistor as a common emitter
amplifier. Figure 3-5 shows which crosspoints to close to
configure the amplifier circuit. In this circuit, gain is calcu-
lated by dividing collector current (measured by the Model
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