Electronic Devices 1- Semicon To Diodes Flashcards
A silicon diode measures a low value of resistance with the meter leads in both positions. The trouble, if any, is
the diode is open.
the diode is shorted to ground.
the diode is internally shorted.
the diode is working correctly.
the diode is internally shorted.
Single-element semiconductors are characterized by atoms with ____ valence electrons.
3
4
5
2
none of the above
4
Under normal conditions a diode conducts current when it is
reverse-biased.
forward-biased.
avalanched.
saturated.
forward-biased
A diode conducts when it is forward-biased, and the anode is connected to the ________ through a limiting resistor.
positive supply
negative supply
cathode
anode
positive supply
As the forward current through a silicon diode increases, the internal resistance
increases.
decreases.
remains the same.
decreases
The movement of free electrons in a conductor is called
voltage.
current.
recombination.
equilibrium.
current
For a forward-biased diode, the barrier potential ________ as temperature increases.
decreases
remains constant
increases
decreases
The wide end arrow on a schematic indicates the ________ of a diode.
ground
direction of electron flow
cathode
anode
anode
An n-type semiconductor material
is intrinsic.
has trivalent impurity atoms added.
has pentavalent impurity atoms added.
requires no doping.
has pentavalent impurity atoms added.
For a forward-biased diode, as temperature is ________, the forward current ________ for a given value of forward voltage.
decreased, increases
increased, increases
increased, decreases
decreased, decreases
increased, increases
Which statement best describes an insulator?
A material with few free electrons.
Effectively, how many valence electrons are there in each atom within a silicon crystal?
8
The boundary between p-type material and n-type material is called
a pn junction.
You have an unknown type of diode in a circuit. You measure the voltage across it and find it to be 0.3 V. The diode might be
a germanium diode.
An ideal diode presents a(n) ________ when reversed-biased and a(n) ________ when forward-biased.
open, short
A reverse-biased diode has the ________ connected to the positive side of the source, and the ________ connected to the negative side of the source.
cathode, anode
What types of impurity atoms are added to increase the number of conduction-band electrons in intrinsic silicon?
pentavalent
What factor(s) do(es) the barrier potential of a pn junction depend on?
type of semiconductive material
the amount of doping
the temperature
-all of the above
An atom is made up of
protons.
neutrons.
electrons.
all of the above
Reverse breakdown is a condition in which a diode
is subjected to a large reverse voltage.
There is a small amount of current across the barrier of a reverse-biased diode. This current is called
reverse leakage current.
As the forward current through a silicon diode increases, the voltage across the diode
is relatively constant.
Doping of a semiconductor material means
that impurities are added to decrease the resistance of the material.
The forward voltage across a conducting silicon diode is about
0.7 V
The most common type of diode failure is a(n)
open
What occurs when a conduction-band electron loses energy and falls back into a hole in the valence band?
recombination
The maximum number of electrons in each shell of an atom is
2n2 where n is the number of the shell.
A silicon diode is forward-biased. You measure the voltage to ground from the anode at ________, and the voltage from the cathode to ground at ________.
2.3 V, 1.6 V
The term bias in electronics usually means
the value of dc voltages for the device to operate properly.
One eV is equal to ________ J.
1.6 × 10–19
The diode ________.
is the simplest of semiconductor devices
has characteristics that closely match those of a simple switch
is a two-terminal device
-All of the above
What does a high resistance reading in both forward- and reverse-bias directions indicate?
An open diode
Which capacitance dominates in the reverse-bias region?
depletion
What is the state of an ideal diode in the region of nonconduction?
An open circuit
How many orbiting electrons does the germanium atom have?
32
How many terminals does a diode have?
2
What unit is used to represent the level of a diode forward current IF?
mA
The diffused impurities with ________ valence electrons are called donor atoms.
5
In which of the following color(s) is (are) LEDs presently available?
Yellow
White
Orange
All of the above
What is the range of the operating voltage level for LEDs?
1.7–3.3 V
At what kind of operating frequency diffusion or transition is a capacitor represented in parallel with the ideal diode?
Very high frequency
Which of the following devices can check the condition of a semiconductor diode?
Digital display meter (DDM)
Multimeter
Curve tracer
All of the above
Which of the following is an atom composed of?
Electrons
Protons
Neutrons
All of the above
The condition of a semiconductor diode can be determined quickly using a ________.
DDM
VOM
curve tracer
Any of the above
How many valence electrons does a silicon atom have?
4
What is the resistor value of an ideal diode in the region of conduction?
0
Calculate the power dissipation of a diode having ID = 40 mA.
28 mW
Calculate static resistance RD of a diode having ID = 30 mA and VD = 0.75 V.
Using Ohm’ law V= iR.
0.75mV= 40 mA * R.
We gets,
R = 25 V/A,
R = 25 ohms.
In which of the following is the light intensity measured?
Candela
Calculate ID if RD = 30 and VD = 0.84 V.
ID = VD/RD.
ID = 0.84/30.
ID = 0.028 A (Converting A into mA. Then multiply by 1000).
ID = 0.028*1000 = 28 mA.
Which of the following elements is most frequently used for doping pure Ge or Si?
Boron
Gallium
Indium
All of the above
Calculate the temperature coefficient in %/° C of a 10-V nominal Zener diode at 25° C if the nominal voltage is 10.2 V at 100° C.
V1 = 10 V.
T1 = 25 c.
V2 = 10.2 V.
T2 = 100 c.
Then temperature coefficient is = [{(V2-V1)/V1}/(T2-T1)]*100.
= [(10.2-10/10)/(100-25)]*100.
= 0.0267 V.
In general, LEDs operate at voltage levels from ________ V to ________ V.
1,7, 3.3
Determine the nominal voltage for the Zener diode at a temperature of 120° C if the nominal voltage is 5.1 volts at 25° C and the temperature coefficient is 0.05%/° C.
Vf = Vi * [1 + (Coeff / 100)(Tf - Ti)],
Vf = 5.1[1 + (0.05/100)*(120-25)],
Vf = 5.43225 V.
What is the maximum power rating for LEDs?
150 mW
The ________ diode model is employed most frequently in the analysis of electronic systems.
simplified
What is the value of the transition capacitance for a silicon diode when VD = 0? (Choose the best answer.)
3 pF
Which of the following ratings is true?
Si diodes have higher PIV and wider temperature ranges than Ge diodes.
The ideal diode is a(n) ________ circuit in the region of nonconduction.
open
Which capacitance dominates in the forward-bias region?
Diffusion
In what state is a silicon diode if the voltage drop across it is about 0.7 V?
Forward bias
Schottky diodes are also known asSchottky diodes are also known as
hot carrier diodes.
Zener diodes with breakdown voltages less than 5 V operate predominantly in what type of breakdown?
zener breakdown
The Schottky diode is used
in very fast-switching circuits.
You have an application for a diode to be used in a tuning circuit. A type of diode to use might be
a varactor
What kind of diode is formed by joining a doped semiconductor region with a metal?
Schottky
Which diode employs graded doping?
step-recivery
LEDs are made out of
gallium
The normal operating region for a zener diode is the
reverse-breakdown region.
An LED is forward-biased. The diode should be on, but no light is showing. A possible trouble might be
the diode is open.
A 6.2 V zener is rated at 1 watt. The maximum safe current the zener can carry is
Iz=P/Vz
Iz=1/6.2
Iz=0.161A
Iz=161mA
The process of emitting photons from a semiconductive material is called
electroluminescence
What diode operates only with majority carriers?
Schottky
An 8.2 V zener has a resistance of 5. The actual voltage across its terminals when the current is 25 mA is
Vz = 8.2 V.
Rs = 5 ohms.
Is = 25 mA = 0.025 A.
Vs = Is x Rs.
= 0.025 x 5 = 0.125 V.
Vin = Vz+Vs.
= 8.2 V + 0.125 V.
= 8.325 V answer.
What type of diode maintains a constant current?
current regulator
What diode is used in seven-segment displays?
LED
Zener diodes with breakdown voltages greater than 5 V operate predominantly in what type of breakdown?
avalanche
Back-to-back varactor diodes are used for what reason?
to eliminate harmonic distortion
A tunnel diode is used
in circuits requiring negative resistance.
What type of diode is commonly used in electronic tuners in TVs?
varactor
A laser diode normally emits
coherent and monochromatic light.
A varactor is a pn junction diode that always operates in ________-bias and is doped to ________ the inherent capacitance of the depletion region.
reverse, maximize
What type of diode circuit is used to clip off portions of signal voltages above or below certain levels?
clipper or limiter
Each diode in a center-tapped full-wave rectifier is ________ -biased and conducts for ________ of the input cycle.
forward, 180º
The output frequency of a full-wave rectifier is ________ the input frequency.
twice
PIV is which of the following?
peak inverse voltage
In a regulated supply, what term describes how much change occurs in the output voltage for a given change in the input voltage?
line regulation
A short circuit has a ________ drop across its terminals, and the current is limited only by the surrounding network.
0 V
What type of diode circuit is used to add or restore a dc level to an electrical signal?
clamper
In a regulated supply, what term describes how much change occurs in the output voltage over a certain range of load current values, from minimum to maximum current?
load regulation
What is the PIV for each diode in a full-wave center-tapped rectifier? Note: Vp(out) = peak output voltage.
2Vp(out) + 0.7 V
If the ac supply is 50 Hz, what will be the ripple frequency out of the full-wave rectifier?
100 Hz
How many terminals do the 7800 series fixed positive voltage regulators have?
3
An open circuit can have any voltage across its terminals, but the current is always ________.
0 A
A silicon diode in a half-wave rectifier has a barrier potential of 0.7 V. This has the effect of
reducing the peak output voltage by 0.7 V.
In the operation of a half-wave rectifier with a capacitor-input filter, the ripple factor can be lowered by ________ the value of the filter capacitor or ________ the load resistors.
increasing, increasing
In a particular problem, which mode has the highest level of IDQ?
Ideal
Which diode(s) has (have) a zero level current and voltage drop in the ideal model?
Both Si and Ge
The output frequency of a half-wave rectifier is ________ the input frequency.
equal to
A diode is in the “________” state if the current established by the applied sources is such that its direction matches that of the arrow in the diode symbol, and VD ≥ 0.7 V for Si and VD ≥ 0.3 V for Ge.
on
List the categories of clippers.
Series and parallel
A silicon diode has a voltage to ground of –117 V from the anode. The voltage to ground from the cathode is –117.7 V. The diode is
forward-biased.
In a voltage regulator network with fixed RL and R, what element dictates the minimum level of source voltage?
Vz
