CHAPTER 16 ■ TRANSISTOR SWITCHES- With a pair of transistor leads at a time, connect each of the leads to the
multimeter test probes and write down the value. For example, connect the
transistor’s first lead to the red test probe and connect the transistor’s second
lead to the black test probe and record the value. - Continue until you’ve tested all lead combinations as shown in the first column
of Table 16-2.
Of all the combinations, only two should have a voltage drop of between 0.5 and 0.7. All of the other
combinations should be infinity. Sample results appear in Table 16-2.
Figure 16-4. Setting up a multimeter for testing a transistor with the diode test function
Table 16-2. Example Diode Test Results for Two Different Bipolar Transistor Types
Leads Sample PNP Sample NPN
1 red & 2 black 0.623 V infinity
1 red & 3 black infinity infinity
2 red & 3 black infinity 0.606 V
2 red & 1 black infinity 0.610 V
3 red & 1 black infinity infinity
3 red & 2 black 0.619 V infinity