Industrial Sensing Fundamentals – Back to the Basics: NPN vs PNP

Written by: Andrew Bollinger

What’s the difference and why should anyone care? If you’re confused by the terms PNP and NPN, then hopefully this post will shed some light on the differences between the two.  In the context of this post, they refer to the construction of a sensor’s transistor and whether it has a p-type or n-type semiconductor.

When it comes to wiring a sensor, you can think of the “N” as standing for “Negative” and the “P” as standing for “Positive”. With respect to sensors, an NPN device is one that can switch the negative side of the circuit while a PNP device switches the positive side.

The next question to ask is, what direction do you want the current to flow?

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