MOSFETs? I
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.
QUESTION 2
a) How would you characterise power bipolar devices in comparison with power
MOSFETs? Illustrate your answer by providing unique features of power MOSFETs.
b) Using the aid of a MOSFET diagram, explain operational features of the power
MOSFET. Support your explanation using MOSFET operation as a switch. Also,
illustrate the conditions needed to drive a power MOSFET in the different regions of
operation.
c) Discuss four (4) advantages of a bridge or half-bridge forward converter when compared
with a single-ended forward converter
Step by step
Solved in 2 steps
