(a) For both power BJT and Power MOSFET as shown in Fig. Q2(a) is driven into complete saturation mode with saturation current 20A. Explain the reasons why power MOSFET exhibits lower power handling capability as compare with power BJT. (i) (ii) Ignoring the base current, Ig. Calculate the power consumption of the power BJT and Power MOSFET. Drain Gate Sourceo HE Ed Iccsat) = 20A VCE(Sat) = 1.2V Ios(sat) = 20A Channel resistant, rps = 0.1A Fig. Q2(a)
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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