State the full form of MOSFET
Metal oxide field effect transistor
How many
terminals the MOSFET consists of?
Three terminals : Source, Drain and
Gate
Describe
the main advantage of the Power MOSFET over other semiconductor devices.
Advantages of the MOSFET
Low input power
High switching speed
Whether
the MOSFET is voltage controlled or current controlled device? Why?
Voltage
controlled device
The MOSFET is a voltage-controlled
majority charge carrier device in the output current is controlled by the input
voltage. The conduction of current in the n channel MOSFET is done only by
electrons whereas the current conduction in the p channel is done by holes.
What is reason
behind the name MOSFET?
The majority charge carriers in the
MOSFET are controlled by gate voltage. The gate is insulated by metal oxide
layer therefore it is called as MOSFET.
Describe
the different types of MOSFET.
Types of MOSFET
Depletion enhancement MOSFET ( 1 ) N
channel and ( 2 ) P channel
Enhancement MOSFET ( 1 ) N channel
and ( 2 ) P channel
Which is
the operating mode of the Depletion enhancement ( DE ) MOSFET?
The operating mode of DE MOSFET
Depletion mode
Enhancement mode
Whether
the MOSFET is operated at low voltage?
No, the MOSFET is
not operated below 500 Voltage.
What do
you mean by the Depletion mode and Enhancement mode in the MOSFET?
Depletion mode
When the negative gate to source
voltage is applied to N channel MOSFET, it is called as depletion mode of the
MOSFET.
Enhancement mode
When the positive gate to source
voltage is applied to N channel MOSFET, it is called as enhancement mode of the
MOSFET.
Why the
vertical structure of the MOSFET is used?
The vertical structure of the MOSFET
is used in order to achieve
High current rating and
High break down voltage
Whether
the doping level in the P type material and N type material is same in the N
channel MOSFET?
Doping
level
The two ends n+ type
material is heavily doped whereas the middle P type material is moderately
doped in the N channel MOSFET. The n- drift layer has lowest doping
level.
Which
parameter greatly affects the breakdown voltage of the n channel MOSFET?
n- drift drain layer
Which
parameter affects the ON state resistance of the MOSFET?
Geometric shape of source regions
In which
type of MOSFET, there is no physical channel?
Enhancement MOSFET
Explain
the term : Cut off region and ohmic region
Cut
off region
When the gate to source voltage is
less than the threshold voltage, the MOSFET is operated in the cut off region.
The applied voltage must be less than the break down voltage of the MOSFET. No
drain current flows.
Ohmic
region
The MOSFET is operated in the ohmic
region when the gate to source voltage is greater than the gate to source threshold
voltage ( VGS > VGS
(TH) ).
The drain current is almost directly
proportional to drain to source voltage for small value drain to source
voltage.
In which
region, the power dissipation is very high in the MOSFET?
Active region
Give
reason : There is no current flow between drain to source in the MOSFET without
gate bias.
The current does not flow between drain
to source in the MOSFET without gate
bias due to two back-to-back PN junction diode
Describe
the disadvantage of the planner type MOSFET construction.
The planner type construction has
long source to drain channel therefore large on state resistance.
Which are
the resistances present in the internal circuit of the MOSFET?
Internal resistance in
the MOSFET
Source region resistance
Drift region resistance
Drain resistance and
Channel resistance
Describe
the effect of gate to source voltage on the on-state drain to source
resistance.
As the gate to source voltage
increases, the on-state drain to source resistance decreases and vice versa.
What is
main reason for switching delay in the MOSFET?
The main reason for switching delay
is due to charging and discharging of input and output capacitors in the
MOSFET.
Give
reason : The parallel connection of the MOSFET is easily done.
The on-state resistance of the MOSFET
has positive temperature co – efficient therefore the parallel connection is
easily done.
Why the
switching speed of the Power MOSFET is higher than the bipolar transistors?
Switching speed
The Power MOSFET is a unipolar
device.
The current conduction is done
through only majority charge carriers. The turn off delay does not occur due to
recombination of minority charge carriers. Therefore, the speed of the Power
MOSFET is higher than the bipolar transistors.
State the
applications of the Power MOSFET.
Applications
of Power MOSFET
Speed control of ac and dc motors
Switching device in stepper motor
controllers
Lighting control
Medical equipment
Relays
Induction heating
Robotics
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