PEI Exam 1
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(T/F) A diode is forward-biased if the diode's anode is at a higher potential than the diode's cathode
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(T/F) All academic misconduct, including "minor" and first-time offences will be reported to the Dean
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(T/F) An intrinsic semiconductor has an equal number of free electrons and holes.
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(T/F) Both n- and p-material are electrically neutral. The "n" and "p" designations merely refer to the dominant type of charge carriers in the material
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(T/F) Holes are less mobile than electrons and in an applied electric field they experience a force in the same direction as the field
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(T/F) Holes travel in the opposite direction of the electric field.
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(T/F) Intrinsic semiconductor material has no charge, but doped semiconductor materials have charge according to their type: p-type has positive charge and n-type has negative charge
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(T/F) One can increase the size of the depletion region of a pn-junction by reverse-biasing the junction.
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(T/F) One can use a LED as a photodetector in some instances
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(T/F) Photocurrents flow the same direction as diode's polarity, from cathode to anode.
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(T/F) The electrical resistance of an p-type semiconductor increases with increasing temperature
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(T/F) The electrical resistance of n-type semiconductor decreases with increasing temperature
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(T/F) The so-called thermal voltage in semiconductor theory increases with increasing temperature.
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(T/F) When a pn-junction diode is forward-biased, the depletion region is larger than without the forward bias, and consequently current can flow through the diode
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(T/F) When a pn-junction diode is foward-biased, the depletion region is larger than without the forward bias, and consequently current can flow through the diode.
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(T/F) n-Type semiconductor material is negatively charged and p-type semiconductor material is positively-charged
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(T/F) turn-on voltages of red LEDs are smaller than the turn-on voltage of blue LEDs
positive power supply
A diode conducts when it is forward-biased, and the anode is connected to the ________ through a current-limiting resistor.
Diffusion
A semiconductor rod is illuminated with light with a wavelength short enough to generate excess carriers at x = 0. The applied electric field is zero. The excess carriers flow from left to right in the rod and this constitutes an electric current that is called a ________ current?
the diode is broken and internally open
An engineer tests a silicon diode with a multimeter using the Ohm-meter function. The meter measures a high value of resistance with the meter leads in both positions. The trouble, if any, is that.....
the diode is broken and internally shorted
An engineer tests a silicon diode with a multimeter using the Ohm-meter function. The meter measures a low value of resistance with the meter leads in both positions. The trouble, if any, is that.....
decreases
Forward bias voltage ______________ with increasing temperature.
4
How many valence electrons do germanium atoms have?
photon
In LEDs, the recombination of an electron and hole forms a __________.
+-2%
In the past, multimeters were expensive and were sometimes not very accurate. However, even inexpensive modern multimeters, typically have accuracies of....
Drift current
Movement caused by electric fields
voltage
On an oscilloscope the horizontal axis represents time, and the horizontal voltage represents
peak inverse voltage
PIV stands for ________________
decreases
Reverse saturation current decreases as temperature ___________.
larger
Schottky diode's reverse saturations are much ____________ that that of Si pn-junction diodes.
smaller
Schottky diodes' turn on voltages are much ___________ than those of Si pn-junction diodes.
n
Silicon is doped with arsenic atoms. Is this n- or p-type silicon?
p
Silicon is doped with boron atoms. Is this n- or p-type silicon?
cathode
The band on the body of a diode normally indicates the __________ of the diode.
Diffusion current
The flow caused by variations in the concentration, e.g. concentration gradients
5%
The gold band on a resistor indicates that the tolerance of the resistor is __________.
60
The line frequency of the power supply is 60 Hz, which is stepped down and rectified with a half-wave rectifier. What is the frequency of the load voltage?
Holes
The majority carrier of a p-type semiconductor.
Electrons
The majority carrier of an n-type semiconductor.
carbon film resistors
The type of resistors that are most widely-used (such as those measured in the first lab) are....
Ge, Doped Si, Si, Doped Ge
Type all the elemental semiconductor materials from list: (Ge, Doped Si, Si, SiC, GaAs, Doped Ge, GaP)
26mV
What is the approximate value of the thermal voltage at 300 K?
V^-1
What is the correct units for the term q/kT, which often appears in equations that describe semiconductor materials and components?
metallurgical junction
What is the interface at x=0 called in a pn-junction.
Trivalent
What type of atoms are added to molten silicon in order to create p-type semiconductor material?
Pentavalent
What type of atoms are added to molten silicon in order to increase the number of free electrons?
RMS Voltage
When a multimeter is on the ac voltage setting, it will measure the....
maximum rating
When a pn-junction diode experiences reverse breakdown the diode is not damaged as long as the current through the diode is below its ____________ ___________.
mean
When excess carriers are created in a semiconductor (by exposing it to a light pulse for example) the holes and electrons recombine and the excess carriers disappear after some time. The excess carrier lifetime is a measure of how quickly this recombination takes place, and it is the _______ time over which an excess electron and hole exists before recombination.
Top
When looking at the forbidden bandgap, is the conduction band on top or on bottom?
positive
When measuring resistance/continuity or testing diodes, the meter will force a small current out of the red terminal. That is, the red terminal is (slightly) more ___________ than the black terminal
capacitor
When one selects AC coupling on an oscilloscope, a _____________ is placed in series with the input and this removes the dc component of the input signal so that only the ac part is shown on the screen.
IR < red < green < UV
put the following LEDs in order of turn-on voltages, from lowest to highest using < to separate them: (green, UV, IR, red)
