Polarity identification and quality testing of 2

(2) After finding the discrimination base for the emitter and collector, in the remaining two pins, one is the collector C; the other is the emitter Ea. Pinch the base and the pin to be judged together by hand, but do not touch each other. This is equivalent to connecting a resistor of several tens of kiloohms between the base and the pin to be tested. Use a red meter rod to contact the pin pinched together with the base, as shown in Figure 5-77 (a). transistor Use a black meter rod to contact the other pin to be judged, measure the resistance value, swap the two pins to be judged, and test again. In the smaller of the two tests, the pin that the black meter rod contacts is the one with the smaller resistance value. The emitter, and the other pin to be tested is the collector. Because the black meter rod is actually the negative pole of the internal power supply of the multimeter, as shown in Figure 5-77 (b).transistor  After connecting a resistor in series between the collector and base, connect the black meter rod to the emitter and the red meter rod to the collector. transistorThis is a form of common emitter circuit. Due to the emitter junction being under forward voltage and the collector junction being under reverse voltage, most of the emitter current flows to the collector, indicating that the resistance between the emitte r and collector is very small. On the contrary, the emitter junction is in a reverse voltage state, so there is no base current, and the resistance between the collector and emitter is very high, as shown in Figure 5-77 (c).transistor