Multimeter Tutorial: How to Test a Transistor


This tutorial will detail with testing PNP and NPN configured transistors using a multimeter. After reading this, you will be able to find out configuration of the device as well as find out its collector, emitter and base.1

 Step 1:Transistor Function on Multimeter.


If the model number is not known, it is impossible to detail about the  type of transistor just by looking at it. To ease the process, multimeters come with a function where one can calculateHfe or small signal Forward Current Gain of a bipolar transistor.

Apart, from detailing with the forward gain value, the Hfe function solves two problems.

  • {C}{C} {C}{C}Type of the transistor can be found.
  • {C}{C} {C}{C}Collector, Base, Emitter terminals can also be known.

 Step 2:Checking Transistor

  1.   a) Testing an  NPN Transistor                                                                             3
  • Place the three legs of the Transistor first in the E-B-C formation. The multimeter will show the reading if this formation is correct, else it will show over range.
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  • If the previous method doesn’t work, place the three legs of the Transistor in the B-C-E formation. If multimeter shows reading then it’s correct. The reading is nothing but thr HFE of that transistor.


  1.       b)Testing  PNP Transistor .
  2. 5
  • Place the three legs of the transistor in the same manner as discussed above.
  • After placing the transistor in the correct formation, multimeter would show the Hfevalue of the transistor.
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  • How to Test a Transistor using Multimeter

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