The right way to select MOSFETs

Post Time: May-20-2024

Select the correct MOSFET for the circuit driver is a very important part of the MOSFET selection is not good will directly affect the efficiency of the entire circuit and the cost of the problem, the following we say a reasonable angle for the MOSFET selection.

1, N-channel and P-channel selection
(1), In common circuits, when a MOSFET is grounded and the load is connected to the trunk voltage, the MOSFET constitutes a low voltage side switch. In a low voltage side switch, an N-channel MOSFET should be used, due to considerations of the voltage required to turn off or turn on the device.

(2), when the MOSFET is connected to the bus and the load is grounded, a high voltage side switch is to be used. P-channel MOSFETs are usually used in this topology, again for voltage drive considerations.

2, want to choose the right MOSFET, it is necessary to determine the voltage required to drive the voltage rating, as well as in the design of the easiest way to implement. When the rated voltage is greater, the device will naturally require a higher cost. For portable designs, lower voltages are more common, while for industrial designs, higher voltages are required. With reference to practical experience, the rated voltage needs to be greater than the trunk or bus voltage. This will provide sufficient safety protection so that the MOSFET will not fail.

3, followed by the structure of the circuit, the current rating should be the maximum current that the load can withstand under all circumstances, which is also based on the safety of the necessary aspects to consider.

4. Finally, the switching performance of the MOSFET is determined. There are many parameters that affect switching performance, but the most important are gate/drain, gate/source and drain/source capacitance. These capacitances create switching losses in the device because they have to be charged during each switch.