Bipolar transistors

In the circuit symbol of an NPN transistor, which way does the arrow on the emitter point?

  1. AFrom the collector toward the emitter
  2. BOutward, from the base out through the emitter
  3. CInward, from outside the emitter toward the base
Show answer and explanation

Answer: B. Outward, from the base out through the emitter

The arrow in the symbol shows the direction of forward current through the base-emitter PN junction. In an NPN transistor, current flows from the base (p) to the emitter (n), so the arrow points outward on the emitter. In a PNP transistor it points inward.

  • A. The arrow shows the base-emitter forward current; it is unrelated to the collector.
  • B. Correct. In an NPN transistor the arrow points out of the emitter.
  • C. An arrow pointing inward toward the base is the PNP symbol.
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More Bipolar transistors questions

  1. Which correctly relates the emitter current IE, base current IB and collector current IC of a bipolar transistor?
  2. A transistor with DC current gain hFE = 100 has a base current of 10 μA. Roughly what is the collector current in the active region?
  3. What is the state of the junctions when a bipolar transistor is in the cutoff region (off)?
  4. What is the typical base-emitter voltage VBE of a silicon bipolar transistor operating in the active region?
  5. What is the collector dissipation of a transistor operating at a collector-emitter voltage of 5 V and a collector current of 100 mA?