Test with a multimeter

Darlington (TIP120)

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Now: Base → emitter: two thresholds

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Pin 1: Base (B) (B) Pin 2: Collector (C) (C) Pin 3: Emitter (E) (E)

Red probe Not connectedBlack probe Not connected

Hold the probe and drag it to the tip of a leg. Tapping works too: first pick the probe, then the leg.

Set the range to diode test.

Measure step by step

A Darlington transistor contains two transistors; between base and emitter there are two thresholds and two small resistors, and between collector and emitter there is a protection diode in the opposite direction (the TIP120 has one). So the values differ from a single transistor. This guide uses the TIP120 pin order.

  1. 1Base → emitter: two thresholds
  2. 2Base → collector
  3. 3Emitter → collector: protection diode
  4. 4Collector → emitter
  5. 5Base-emitter resistance (Ω)