Which two transistor types are commonly used in sensors?

Which two transistor types are commonly used in sensors?

• A. NPN and PNP
• B. N-channel MOSFET and P-channel MOSFET
• C. JFET and MOSFET
• D. BJT and MOSFET

Answer: (A)

The main idea is that sensor outputs are often designed to either pull the load to ground or push current from the supply. NPN and PNP transistors provide these two complementary output modes, making it easy to wire sensors to PLC inputs and other loads. An NPN (sinking) output pulls the load toward ground when active, while a PNP (sourcing) output supplies current from the positive supply to the load. This complementary pairing is widely used because it offers flexible wiring, compatibility with a broad range of controllers, and reliable, cost-effective performance in many automation environments. Other transistor types exist, like MOSFET-based outputs, but the traditional and most common sensor outputs are the NPN and PNP pair.

The main idea is that sensor outputs are often designed to either pull the load to ground or push current from the supply. NPN and PNP transistors provide these two complementary output modes, making it easy to wire sensors to PLC inputs and other loads. An NPN (sinking) output pulls the load toward ground when active, while a PNP (sourcing) output supplies current from the positive supply to the load. This complementary pairing is widely used because it offers flexible wiring, compatibility with a broad range of controllers, and reliable, cost-effective performance in many automation environments. Other transistor types exist, like MOSFET-based outputs, but the traditional and most common sensor outputs are the NPN and PNP pair.