What are the two transistor types used in sensors?

What are the two transistor types used in sensors?

• A. PNP and NPN
• B. MOSFET and IGBT
• C. BJT and JFET
• D. SCR and TRIAC

Answer: (A)

Sensors commonly use PNP and NPN transistor outputs. This pairing defines how current flows when the sensor is active, which is crucial for wiring to PLC inputs. A PNP output sources current from the positive supply through the transistor to the load, so the load receives current when the sensor activates. An NPN output sinks current, pulling the load toward ground when active, with the load connected to the supply side ahead of the sensor. This sourcing versus sinking behavior is what you match to the PLC input configuration to ensure proper operation. Other devices mentioned are power switching transistors or switches used in different contexts, not the standard sensor outputs used with PLCs.

Sensors commonly use PNP and NPN transistor outputs. This pairing defines how current flows when the sensor is active, which is crucial for wiring to PLC inputs. A PNP output sources current from the positive supply through the transistor to the load, so the load receives current when the sensor activates. An NPN output sinks current, pulling the load toward ground when active, with the load connected to the supply side ahead of the sensor. This sourcing versus sinking behavior is what you match to the PLC input configuration to ensure proper operation. Other devices mentioned are power switching transistors or switches used in different contexts, not the standard sensor outputs used with PLCs.