EDC 1 Flashcards
Which of the following does not result
from adding an acceptor impurity?
A. The substance has an electron
surplus
B. Most of the carriers have positive electric
charge
C. The material becomes P type
D. Current flows mainly in the form of holes
A. The substance has an electron
surplus
Acceptor impurities are trivalent atoms
or atoms having 3-valence electrons
such as Boron, Indium, Gallium, and Aluminum are trivalent impurities.
If acceptor impurities were added to a pure semiconductor material, the result will be a greater increase in the number of holes compared to the number of free electrons.
This will make the material to have greater number of positive electric charges making the
resulting extrinsic semiconductor a P-type.
And finally in a P-type semiconductor current flows mainly in the form of holes, since holes are the majority carriers.
In “p” type material, minority carriers
would be:
A. holes
B. dopants
C. slower
D. electrons
D. electrons
In a P-type material:
Majority carriers → holes
Minority carriers → free electrons
In an N-type material:
Majority carriers → free electrons
Minority carriers → holes
Which of the following will make the
statement TRUE. In pure silicon _____
A. the holes and electrons exist in
equal numbers
B. the electrons are the majority carriers
C. the holes are the majority carriers
D. conduction is due to there being more
electrons than holes
A. the holes and electrons exist in
equal numbers
“pure” means that the semiconductor
material is an INTRINSIC one. And, in an intrinsic semiconductor, the number of free electrons and holes are equal.
A pure semiconductor is often referred
to as a (n)
A. Doped semiconductor
B. Intrinsic semiconductor
C. Extrinsic semiconductor
D. None of these choices
B. Intrinsic semiconductor
An intrinsic semiconductor, also called
an undoped semiconductor or i-type
semiconductor, is a pure semiconductor
without any significant dopant species
present. The number of charge carriers
is therefore determined by the
properties of the material itself instead
of the amount of impurities.
An n-type semiconductor is a
semiconductor that has been doped
with
A. Impurity atoms whose electron valence is
+4
B. Pentavalent impurity atoms
C. Trivalent impurity atoms
D. None of these choices
B. Pentavalent impurity atoms
PENTAVALENT atoms (with 5 valence
electrons) called DONOR impurities
such as Phosphorous, Antimony,
Arsenic, and Bismuth are used in doping
process to create an N-type
semiconductor. On the other hand,
TRIVALENT atoms (with 3 valence
electrons) called ACCEPTOR impurities
such as Boron, Indium, Gallium, and
Aluminum are used as dopants to
create a P-type semiconductor.
What electrical characteristic of intrinsic semiconductor material is controlled by the addition of impurities?
A. conductivity
B. all of these choices
C. voltage
D. power
A. conductivity
Adding impurities (either DONOR or
ACCPETOR) will increase the number of
charge carriers (either HOLES or FREE
ELECTRONS) in the semiconductor
material. This increase in charge carrier will then make the material more likely to conduct current, therefore the conductivity changes.
A silicon diode measures a low value of resistance with the meter leads in both positions. The trouble, if any, is
A. the diode is working correctly.
B. the diode is internally shorted.
C. the diode is open
D. the diode is shorted to ground
B. the diode is internally shorted.
A good diode will indicate a very low resistance in one direction and a very high resistance in the other direction.
The process of adding impurity atoms
to a pure semiconductor is called
A. recombination
B. crystallization
C. bonding
D. doping
D. doping
DOPING: Doping is the process of adding
impurities to intrinsic semiconductors to alter
their properties.
CRYSTALLIZATION: Crystallization or crystallisation is the (natural or artificial)process by which a solid forms.
BONDING: Bonding refers to the attraction
between atoms, ions or molecules that
enables the formation of chemical compounds.
RECOMBINATION: Recombination is the
process wherein free electron falls back to a
hole (vacancy of electron in the valence
shell).
An n-type semiconductor material
A. has trivalent impurity atoms added
B. is intrinsic.
C. requires no doping.
D. has pentavalent impurity atoms added.
D. has pentavalent impurity atoms added.
N-type semiconductor material, is an
extrinsic semiconductor material that is
the product of doping process that
involves adding donor impurities/
pentavalent atoms such as
Phosphorous, Antimony, Arsenic, or
Bismuth to an intrinsic Silicon or Germanium.
The amount of time between the
creation of a hole and its disappearance
is called
A. Recombination
B. Lifetime
C. Valence
D. Doping
B. Lifetime
The average timing between the
creation and the disappearing of an
electron-hole pair is termed as Lifetime.
The lifetime varies from nanoseconds to
several microseconds depending
upon the various factors such as shape,
size, crystal structure of the
semiconductor material.
When the reverse voltage increases, the
capacitance
A. Has more bandwidth
B. Increases
C. Stays the same
D. Decreases
D. Decreases
When the reverse voltage increases,
depletion region of a diode also
increases. Since the capacitance of the diode is inversely related to this size of depletion region, the capacitance of the diode will therefore decrease.
The most commonly used
semiconductor material is
A. silicon
B. germanium
C. mixture of silicon and germanium
D. none of these choices
A. silicon
In relation to semiconductor materials,Silicon is the most commonly used due to the reason that it is more abundant compared to other semiconductor materials.
It is even the most common element in the Earth’s crust.
The abundance of Si allows it to be
extremely affordable and appealing.
Applying voltage to a PN junction is called:
A. doping.
B. temperature.
C. biasing.
D. covalent bonding.
C. biasing.
Bias means to apply voltage. Forward biasing will turn on a semiconductor,reverse bias will turn it off.
During reverse bias, a small current
develops known as
A. Break back current
B. Active current
C. Reverse saturation current
D. Forward current
C. Reverse saturation current
When the diode is reverse biased, a
small current flows between the p-n
junction which is of the order of the Pico
ampere. This current is known as
reverse saturation current or
(sometimes) leakage current.
A tunnel diode is used
A. in very fast-switching circuits.
B. in power supply rectifiers.
C. in circuits requiring negative
resistance.
D. in high-power circuits.
C. in circuits requiring negative
resistance.
The tunnel diode characteristics and
operation depend upon some of the
subtle differences between a normal PN
junction and structure of the tunnel
diode itself. Essentially it is the very high doping levels used in the tunnel diode its unique properties and characteristics.
Tunnel diode does not act as a normal diode, but instead exhibits a negative resistance region in
the forward direction.
The I-V characteristic curve, combined with the very high speed of the diode mean that it can be used in a variety of microwave RF applications as an active device.
In ideal diode model diode in forward
bias is considered as a
A. Perfect conductor
B. Perfect insulator
C. Capacitor
D. Resistor
A. Perfect conductor
In ideal diode model the diode is
considered as a perfect conductor in forward bias and perfect insulator in reverse bias. That is voltage drop at forward bias is zero and current through the diode at reverse bias is zero.
An intrinsic silicon sample has 2 million free electrons. The number of holes in the sample is
A. more than 2 million
B. almost zero
C. less than 2 million
D. 2 million
D. 2 million
In intrinsic semiconductor, the number of free electrons is equal to number of holes.
A negative resistance diode commonly
used in microwave oscillators and
detectors, it is sometimes used as
amplifiers. This device is also known as Esaki diode.
A. IMPATT diode
B. varactor diode
C. tunnel diode
D. Schottky diode
C. tunnel diode
A tunnel diode (also known as a Esaki diode) is a type of semiconductor diode that has effectively “negative resistance”due to the quantum mechanical effect called tunneling.
Tunnel diodes have a heavily doped pn junction that is about 10 nm wide. The heavy doping results in a broken band gap, where conduction band electron states on the N-side are more or less aligned with valence band hole states on the P-side.
(look for the symbol at EDC 1 album)
Which symbol is correct for a zener
diode?
(The figure is in EDC 1 album)
A. d
B. c
C. a
D. b
D. b
(a) is for LED
(b) is for Zener diode
(c) is for Photodiode
(d) is for Tunnel diode
When the applied reverse voltage
applied to a pn-junction diode increases
from 5V to 10 V, the depletion layer
_____, making the capacitance of the
diode to_____
A. becomes smaller; increase
B. becomes larger; decrease
C. becomes larger; increase
D. becomes smaller; decrease
B. becomes larger; decrease
When the reverse voltage increases,
depletion region of a diode also increases.
Since the capacitance of the diode is inversely related to this size of depletion region, the capacitance of the diode will therefore decrease.
