A MOSFET with heat sink absorbs a thermal power of 3.5 W. The thermal resistance from junction to ambient is 45°C/W, and the thermal resistance from sink to ambient is 35°C/W. If the maximum junction temperature is 185°C, determine the maximum ambient temperature, Ta and maximum sink temperature, Tg.
MOSFET (Metal Oxide Semiconductor Field Effect Transistor)
MOSFET stands for Metal Oxide Silicone Field Effect Transistor or Metal Oxide Semiconductor Field Effect Transistor. It is a type of IGFET, which means Insulated Gate Field Effect Transistor. A MOSFET has four-terminals namely gate (G), drain (D), source (S), and body (B). The body of the MOSFET is connected to the source terminal and it forms a three-terminal device. It is used in both the analog and digital circuits.
Power MOSFET
The power MOSFET transistor structures are enhancement types. The voltage rating is enhanced in the enhancement-mode MOSFETs by the use of a drift layer. The MOSFET generally contains four layers. The middle layer is the p-type layer also known as the body, whereas the n-type layer is called the drift layer or region. The drift region decides the breakdown voltage, and hence it is the lightly doped region in power MOSFETs. The first and last layers are the n+ layers. The first layer and the last layers are the source and drain layers. The structure of N-channel MOSFET (e-MOSFET) is n+ p n- n+, but the shape of p-channel is the opposite doping shape.
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