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npn vs. pnp outputs

npn vs. pnp outputs

npn vs. pnp outputs

(OP)
I was just wondering what the advantages or diadvantages of each are. Mainly in regards to industrial sensors and controls. Not sure when you would use one over the other. Thanks.

RE: npn vs. pnp outputs

It mostly depends on the tradition of the industry.  PNP comes from the relay logic tradition where relays switch the plus voltage to a common ground.  NPN comes from the electronics industry where it made much more sense to switch loads to ground (NPN transistors).

RE: npn vs. pnp outputs

Yes, that is true. Historically.

These days the PNP is more or less standard in process control. The reasons: A cable shorted to ground does not activate anything - it would in an NPN system. Some guys also think it is easier to fault-find. But I am not so sure about that. Mostly a question of what you are used to.

Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

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