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How to Test a Defective PNP Transistor

Many consumer electronic devices include a PNP transistor, a type of semiconductor component. The term PNP describes the transistor's construction using P- and N-type semiconductor materials. A PNP transistor includes a base made of N-type material, while the transistor's emitter and collector are made of P-type material. The PNP junctions' arrangement consists of two diodes connected with their cathodes facing each other. Use a digital multimeter to easily test a PNP transistor's operation.

Things You'll Need

Digital multimeter

Instructions

- 1
  Turn on the digital multimeter. Connect the black lead to the "COM" jack; connect the red lead to the "VDC" jack. Turn the function selector knob to the "Diode Test" function.
- 2
  Test the transistor's collector/emitter. Place a test lead on each of the transistor's outboard terminals. The meter reading should be "OL," meaning that the resistance is high. Switch the position of the test leads. Measure the resistance again. The reading should again be high. A working PNP transistor will not conduct in either direction at the collector/emitter.
- 3
  Test the transistor's base/emitter junction. Place a test lead on the transistor's center lead. Place the other test lead on one of the outboard transistor leads. The meter reading will either be high "OL" or read about .7. Switch the test leads. Confirm that the new reading is the opposite of the first reading. A properly working PNP transistor will only conduct in one direction at the base/emitter junction.
- 4
  Test the transistor's base/collector junction. Place a test lead on the transistor's center lead. Place the other test lead on the other outboard transistor lead. The meter reading will either be high "OL" or about .7. Switch the test leads. Confirm that the new reading is the opposite of the first reading. A properly working PNP transistor will only conduct in one direction at the base/collector junction.

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