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80 Cards in this Set
- Front
- Back
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The term transistor
was derived from the words |
TRANSfer and resISTOR.
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which gives current carriers
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EMITTER
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which controls the flow of current carrier
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BASE
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which collects the current carriers
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COLLECTOR
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electron flow is always
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toward or against the arrow, just like in the junction diode.
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What was the name of the very first transistor?
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Point-contact
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To properly bias an NPN transistor, what polarity voltage is applied to the collector, and what is its
relationship to the base voltage? |
Positive, more positive.
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Why is conduction through the forward-biased junction of an NPN transistor primarily in one direction, namely from the emitter to base?
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Because the N material on one side of the forward-biased junction is more heavily doped than the
P-material. |
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In the NPN transistor, what section is made very thin compared with the other two sections?
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The P or base section.
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What percentage of current in an NPN transistor reaches the collector?
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98 percent.
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What percentage of current in an NPN transistor reaches the Base?
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2-5%
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dc voltages and currents that exist in the circuit before the application of
a signal are known as? |
QUIESCENT voltages and currents
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used to pass the ac
input signal and block the dc voltage from the preceding circuit |
coupling capacitor (CC)
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In the basic transistor amplifier discussed earlier, what is the relationship between the polarity of the
input and output signals? |
The signals are opposite in polarity or 180 degrees out of phase with each other.
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Which biasing method is the most unstable?
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Base-Current Bias (Fixed Bias)
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What type of bias is used where only moderate changes in ambient temperature are expected?
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Self-Bias
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When is degeneration tolerable in an amplifier?
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When it is necessary to prevent amplitude distortion
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What is the most widely used combination-bias system?
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voltage-divider
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What amplifier class of operation allows collector current to flow during the complete cycle of the
input? |
Class A
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What is the name of the term used to describe the condition in a transistor when the emitter-base
junction has zero bias or is reverse biased and there is no collector current? |
Cutoff
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What two primary items determine the class of operation of an amplifier?
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The amount of bias and the amplitude of the input signal.
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What amplifier class of operation is the most inefficient but has the least distortion?
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Class A.
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used as an audio- and radio-frequency amplifier
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Class A.
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commonly used as a push-pull amplifier to overcome a side effect of class B operation called crossover distortion.
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Class AB.
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used extensively for audio amplifiers that require high-power outputs.
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Class B
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used as a radio-frequency amplifier in transmitters.
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Class C
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is the faithful reproduction of a signal
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Fidelity
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refers to the ratio of output-signal power compared to the total input
power |
efficiency
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H voltage Gain
L Current Gain L Power Gain L Input Resistance H Output Resistance In phase |
Common Base
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M voltage Gain
M Current Gain H Power Gain M Input Resistance M Output Resistance Out of phase |
Common Emitter
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L voltage Gain
H Current Gain M Power Gain H Input Resistance L Output Resistance In phase |
Common Collector
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Absolute Maximum Ratings of the transistor are
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the direct voltage and current values that if exceeded in operation may result in transistor failure.
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"2 N 130 A" Identify the marking of the tranistor.
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2- NUMBER OF JUNCTIONS
N- SEMI-CONDUCTOR 130-IDENTIFICATION NUMBER A-FIRST MODIFICATION |
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What is the greatest danger to a transistor?
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heat
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What method for checking transistors is cumbersome when more than one transistor is bad in a
circuit? |
The substitution method
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a colored dot, usually red, indicates the
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collector
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A basic transistor gain test can be made using
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an ohmmeter and a
simple test circuit |
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When you are testing the gain of an audio-frequency transistor with an ohmmeter, what is indicated by a 10-to-1 resistance ratio?
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Normal gain.
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When you are using an ohmmeter to test a transistor for leakage, what is indicated by a low, but
not shorted, reverse resistance reading? |
leakage
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diode is a PN junction designed to operate in the reverse-bias breakdown region.
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Zener
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The voltage at which the
sudden increase in current occurs is called the? |
BREAKDOWN VOLTAGE.
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accounts for the breakdown below 5 volts; whereas, above 5 volts the breakdown is caused by the avalanche effect
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Zener effect
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band in which the energy level of the electrons is high enough that the electrons will move easily under the influence of an external field
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CONDUCTION BAND
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band in which the energy level is the same as the valence electrons of
the atoms |
VALENCE BAND
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electrons must cross a gap that exists between the valence band energy level and the conduction band
energy level |
FORBIDDEN ENERGY BAND or FORBIDDEN GAP.
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the semiconductor materials used in forming a junction are doped to the
extent of one-thousand impurity atoms for ten-million semiconductor atoms |
TUNNEL DIODE
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is a diode that behaves like a variable capacitor, with the PN junction functioning like the dielectric and plates of a common capacitor
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Varactor
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varactor, the width of the "gap" may be varied. An increase in reverse bias the what width of the gap (d) which what the capacitance (C) of the PN junction
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increases
decreases |
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function as a switch that can turn on or off small or large amounts of power
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Silicon controlled rectifier
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When an SCR is forward biased, what is needed to cause it to conduct?
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A gate signal
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What is the only way to cause an SCR to stop conducting?
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The forward bias must be reduced below the minimum conduction level.
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controls and conducts current flow during both alternations of an ac cycle, instead of only one
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TRIAC
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The TRIAC is similar in operation to what device?
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SCR.
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When used for ac current control, during which alternation of the ac cycle does the TRIAC control
current flow? |
During both alternations.
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What type of bias is required to cause an LED to produce light?
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Forward bias.
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When compared to incandescent lamps, what is the power requirement of an LED?
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Very low.
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In a common anode, seven-segment LED display, an individual LED will light if a negative voltage is applied to what element?
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The cathode
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What is the resistance level of a photodiode in total darkness?
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Very high
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What type of bias is required for proper operation of a photodiode?
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Reverse bias.
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What is a typical light-to-dark resistance ratio for a photocell?
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1:1000
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What semiconductor device produces electrical energy when exposed to light?
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Photovoltaic cell.
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The UJT has how many PN junctions?
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One.
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The area between base 1 and base 2 in a UJT acts as what type of common circuit component?
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Variable resistor.
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The sequential rise in voltage between the two bases of the UJT is called what?
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A voltage gradient.
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What is the normal current path for a UJT?
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From base 1 to the emitter
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What is one of the primary advantages of the FET when compared to the bipolar transistor?
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High input impedance.
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The FET and the vacuum tube have what in common?
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Voltage controls conduction.
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The base of a transistor serves a purpose similar to what element of the FET?
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Gate.
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What are the two types of JFET?
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N-channel and P-channel.
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The source and drain of an N-channel JFET are made of what type of material?
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N-type material.
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What is the key to FET operation?
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Effective cross-sectional area of the channel.
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What is the normal current path in an N-channel JFET?
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From source to drain.
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Applying a reverse bias to the gate of an FET has what effect?
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Source-to-drain resistance increases.
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The input and output signals of a JFET amplifier have what phase relationship?
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They are 180 degrees out of phase.
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When compared to the JFET, what is the input impedance of the MOSFET?
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The MOSFET has a higher input impedance.
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What are the four elements of the MOSFET?
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Gate, source, drain, and substrate.
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The substrate of an N-channel MOSFET is made of what material?
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P-type material.
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In a MOSFET, which element is insulated from the channel material?
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The gate terminal
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What type of MOSFET can be independently controlled by two separate signals?
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The dual-gate MOSFET.
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What is the purpose of the spring or wire around the leads of a new MOSFET?
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To prevent damage from static electricity.
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