This article outlines several practical applications of MOSFETs in electronic circuits, based on real-world project experience. These applications are relevant for hardware engineers, PCB designers, embedded developers, and electronics hobbyists.
Level Shifting or Isolation Circuits
In circuit design, digital signal transmission between subsystems is often required. However, the voltage levels of digital interfaces may differ between systems or devices, necessitating level shifting circuits. While dedicated integrated circuits are available for level shifting or isolation, MOSFETs or bipolar transistors can be used to build cost-effective solutions. Key considerations include voltage levels, MOSFET orientation, bidirectional communication, and data rates, which influence the circuit's design details.
Reverse Polarity Protection Circuits
Power supply interfaces often require protection against reverse polarity to prevent circuit damage. MOSFETs are advantageous for reverse polarity protection due to their low voltage drop compared to traditional diodes. Typically, PMOS transistors are used on the positive rail, while NMOS transistors are used on the negative rail. The gate of the MOSFET requires resistive components, which can also enable soft-start functionality.
Switching Circuits
MOSFETs are commonly used as electronic switches to control power flow. PMOS transistors are typically employed for switching the positive rail, while NMOS transistors are used for the negative rail.
Soft-Start Circuits
In applications where the load has significant capacitance, a soft-start circuit may be necessary to manage inrush current. This can be achieved by incorporating MOSFETs into the switching circuit design.
Logic Level Conversion Circuits
In addition to voltage level shifting, some applications require logic level conversion. Both MOSFETs and bipolar transistors can be used to achieve this functionality, with MOSFET-based designs offering a reliable solution.
Amplification Circuits
VD-MOSFETs with high transconductance can be used to construct amplification circuits. These circuits are suitable for applications requiring signal amplification, with performance verifiable through simulation.
MOSFETs have additional applications beyond those listed here. In high-power circuit designs, it is critical to understand the practical implications and interrelationships of MOSFET parameters to avoid significant issues.
