"' Current Limiting
t,y Curve Trocer
0
'
..
Ic
Jc
..
0
Current Limiting
t,y Curve Trocer
-
Figure 12. Shorted Transistor Curves
7. If the transistor is open, there will be a hori
zontal trace only, since no collector current will
flow. (see Figure 13).
Effects of Curve Tracer Controls
POLARITY switch-If the POLARITY switch is set
to the wrong polarity, the oscilloscope will display
reverse breakdown characteristic of the transistor
base-emitter junction (See Sorting and Matching
Transistors).
For familiarization, check several transistors, plac
ing the POLARITY switch in both the correct and
incorrect positions and observing the results.
SWEEP VOLTAGE control-The SWEEP VOLT
AGE control adjusts the peak collector voltage (Ve)
and, thereby, the horizontal width of the displ
ay
.
Increasing the setting widens the display and may
cause the display to go off-scale. Decrease and
increase the setting of the control and note the effect
upon the display. If increasing the setting drives
the displ
ay
off-scale, recalibrate the oscilloscope
horizontal axis to a higher voltage. As the sweep
voltage is increased, collector breakdown will be
observed on the oscilloscope displ
ay
. The current
limiter in the curve tracer prevents damage to the
transistor. Collector breakdown is observed as a
sharp turn in the curves (sharp increase in collector
current). Most tests are conducted below collector
breakdown voltage. After observing the effects of
collector breakdown, reduce the setting somewhat
below the breakdown point. (Refer to the "Break
down Voltage Measurement" portion of this manual
v-
L.
, .........
I
J
..
Ic
Vtrtlcol
vertical
ined by
position of troct oeterm
centering of oscilloscop•
V
le
J
..
..
..
.
,
....
/
, .........
J
,
........
..
;;
I'+
:
Figure 13. Open Transistor Curves
11