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What is the difference between NPN and PNP?
Tags: FAQ I/O Modules
NPN (Sinking) and PNP (Sourcing) are two types of transistors used for digital outputs. The terms Sinking and Sourcing refer to current flow with respect to the terminal pin on the IO card. A device is called sinking if current flows into the terminal, and is called sourcing if current flows out of the terminal.

  • PNP transistor outputs are called “sourcing outputs” because they source current from the output to the load.

  • NPN transistor outputs are called “sinking outputs” because they sink current from the load into the output.
Content Created by David Franzwa