PNP transistor output sensors are described as which type of current devices?

• A. Sinking
• B. Sourcing
• C. PNP
• D. Open-loop

Answer: (B)

A PNP transistor output sensor is described as a sourcing device because it delivers current to the load from the positive supply. When the PNP transistor turns on, current flows from +V through the transistor and into the load, returning to ground. That flow of current from the supply into the load is what “sources” current. In contrast, an NPN output would pull current from the load down to ground (sinking). Open-loop isn’t about whether the device sources or sinks current, and the PNP label itself describes the transistor type, not the current direction.