2-35
TRANSISTOR JUNCTION RESISTANCE TEST.—An ohmmeter can be used to test a transistor
for leakage (an undesirable flow of current) by measuring the base-emitter, base-collector, and collector-
emitter forward and reverse resistances.
For simplicity, consider the transistor under test in each view of figure 2-19 (view A, view B and
view C) as two diodes connected back to back. Therefore, each diode will have a low forward resistance
and a high reverse resistance. By measuring these resistances with an ohmmeter as shown in the figure,
you can determine if the transistor is leaking current through its junctions. When making these
measurements, avoid using the R1 scale on the meter or a meter with a high internal battery voltage.
Either of these conditions can damage a low-power transistor.
Figure 2-19A.—Testing a transistor's leakage with an ohmmeter. COLLECTOR-TO-EMITTER TEST
Figure 2-19B.—Testing a transistor's leakage with an ohmmeter. BASE-TO-COLLECTOR TEST
