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Quiz 1
Hydrogen in room temp
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A crystal is a metal…
A: if the conduction band and the valence band overlap
Quiz 2
What level of purity of a material is achievable by chemical methods?
A: up to 10^-6
Describe the process of zone refining in a diagram
A: Zone melting (or zone refining or floating zone process) is a group of similar
methods of purifying crystals, in which a narrow region of a crystal is melted, and
this molten zone is moved along the crystal
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Use a diagram
A:

oxygen impurities
What does MOCVD mean?
A: metal organic chemical vapor deposition
What does MBE mean?
A: molecular beam epitaxy
What is a “clean vacuum”?
A: extremely low pressure vacuum(10^-8) with no oil contamination

What is “piezoelectric”?
A: electric field change  size change
Describe on a diagram construction of a quartz resonator
A:

Plot equivalent electric diagram of a quartz resonator
A:

Plot dependence of absolute value of impedance of a quartz resonator vs
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temp
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sensor, infrared camera
PTC
A: defrost windows
Explain thermal runaway process using current/voltage characteristic of NTC thermistor
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I=V/R

Quiz 4
Describe construction of a photoresistor
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coefficient and is more stable
Write dependence of resistance of a photoresistor vs
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A: a hot object is used and electrons move (+=p, -=n) bottom is measured in respect to the
hot probe
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One claimed that photoresisors are fast
while the other said they are slow
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A: also known as a transferred electron device (TED), is a form of diode, a twoterminal passive semiconductor electronic component, with negative resistance,
used in high-frequency electronics
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Discuss construction of a semiconductor Peltier effect heat pump
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The amount
of heat that can be absorbed is proportional to the current and time
Why reducing crystilite size down to nm range improves performance of Peltier
coolers/and thermoelectric generators
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6 for silicon) (0
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temperature
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voltage characteristic of the backward diode
A:

What can you tell about switching speed of the backward diode
A: the switching speed is fast
What are applications of the backward diodes?
A: signal detector, signal rectifier, switch
Plot current vs voltage characteristic of a tunnel diode
A:

Describe construction and operation of a varistor
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Mark
approximate voltages and currents assuming β=100
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Mark emitter and collector currents assuming β=100
A:

Draw collector current vs collector emitter voltage for npn transistor operating in
common emitter
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A:

A: no because
Quiz 10
Draw a family of characteristics Ic vs Vce of a npn transistor for several different base
currents on a log plot
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In a power transistor with a large
junction area, under certain conditions of current and voltage, the current
concentrates in a small spot of the base-emitter junction

High power low impedance loudspeaker
A; common collector, matches load impedance
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A: A transistor goes into saturation when both the base-emitter and base-collector
junctions are forward biased, basically

Quiz 11:
Describe break down of a transistor operating in CB
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Describe breakdown of a transistor operating in CE
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A:

Explain advantages of a transistor operating in class B over A
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A: more efficient than analog amplifiers and less power dissipated as heat
Draft a large signal(Ebers-Moll) equivalent diagram of the transistor
A:

Explain differences between the Ebers-Moll model and the small signal model of the
transistor
A: on ebers moll inputs and outputs can exceed certain limits
Draft cross section of an SCR and the equivalent diagram of SCR
A:

Quiz 12:
Draw current vs voltage characteristics of a triac
A:

What are MT1 and MT2 in a triac? Which is closest to the gate?
A: MT1, main terminal 1 and 2
Describe inputs to the gate that would trigger a triac for all possible voltage combos
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gate voltage for a n
channel enhancement MOSFET
A:

Your colleague is looking around for enhancement type n channel jfet

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