BJT MCQ Quiz

PNP transistor meter check: (a) forward B-E, B-C, resistance is low; (b) reverse B-E, B-C, resistance is ∞

Bipolar transistors are constructed of a three-layer semiconductor “sandwich,” either PNP or NPN. As such, transistors register as two diodes connected back-to-back when tested with a multimeter’s “resistance” or “diode check” function as illustrated in Figure below. Low resistance readings on the base with the black negative (-) leads correspond to an N-type material in the base of a PNP transistor. On the symbol, the N-type material is “pointed” to by the arrow of the base-emitter junction, which is the base for this example. The P-type emitter corresponds to the other end of the arrow of the base-emitter junction, the emitter. The collector is very similar to the emitter and is also a P-type material of the PN junction.

Read the complete article on BJT meter check here.

The ratio of collector current to emitter current, α=I_C/I_E .   α may be derived from β, being α=β/(β+1)

Base-emitter forward voltage drop, kV_BE , is similar to that of an equivalent diode, ≅0.7 V, which should come as no surprise. Read more about Transistor ratings here.