Login or Register for FREE!
Subelement L03
Semiconductors.
Section L03
What two elements widely used in semiconductor devices exhibit both metallic and non-metallic characteristics?
  • Galena and germanium
  • Galena and bismuth
  • Silicon and gold
  • Correct Answer
    Silicon and germanium

The most basic semiconductor materials are silicon and germanium. Atoms in metallic elements hold their peripheral electrons loosely, such materials make good conductors. Peripheral electrons in non-metallic elements are tightly bound, such materials are insulators. Germanium and silicon fall somewhere between the two categories but are mostly insulators when pure. Doping with impurities increases their conductivity.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In what application is gallium-arsenide used as a semiconductor material in preference to germanium or silicon?
  • In bipolar transistors
  • Correct Answer
    At microwave frequencies
  • In high-power circuits
  • At very low frequencies

Gallium arsenide (GaAs) devices can work at higher frequencies with less noise than their silicon counterparts.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What type of semiconductor material contains fewer free electrons than pure germanium or silicon crystals?
  • N-type
  • Bipolar type
  • Superconductor type
  • Correct Answer
    P-type

Pure germanium and silicon are doped with impurities to produce the basic semiconductor materials. Certain doping impurities add free electrons, forming N-Type material while others accept electrons, thus creating 'holes' found in P-Type material.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What type of semiconductor material contains more free electrons than pure germanium or silicon crystals?
  • Bipolar
  • Superconductor
  • Correct Answer
    N-type
  • P-type

Pure germanium and silicon are doped with impurities to produce the basic semiconductor materials. Certain doping impurities add free electrons, forming N-Type material while others accept electrons, thus creating 'holes' found in P-Type material.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What are the majority charge carriers in P-type semiconductor material?
  • Free electrons
  • Free protons
  • Free neutrons
  • Correct Answer
    Holes

P-Type material was robbed of free electrons, positive 'holes' are the electric charge carriers. N-Type material comprises extra electrons which serve as the electric charge carriers.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What are the majority charge carriers in N-type semiconductor material?
  • Free neutrons
  • Correct Answer
    Free electrons
  • Holes
  • Free protons

N-Type material comprises extra electrons which serve as the electric charge carriers. P-Type material was robbed of free electrons, positive 'holes' are the electric charge carriers.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Silicon, in its pure form, is:
  • Correct Answer
    an insulator
  • a superconductor
  • a semiconductor
  • a conductor

The most basic semiconductor materials are silicon and germanium. Atoms in metallic elements hold their peripheral electrons loosely, such materials make good conductors. Peripheral electrons in non-metallic elements are tightly bound, such materials are insulators. Germanium and silicon fall somewhere between the two categories but are mostly insulators when pure. Doping with impurities increases their conductivity.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

An element which is sometimes an insulator and sometimes a conductor is called a:
  • P-type conductor
  • Correct Answer
    semiconductor
  • intrinsic conductor
  • N-type conductor

The most basic semiconductor materials are silicon and germanium. Atoms in metallic elements hold their peripheral electrons loosely, such materials make good conductors. Peripheral electrons in non-metallic elements are tightly bound, such materials are insulators. Germanium and silicon fall somewhere between the two categories but are mostly insulators when pure. Doping with impurities increases their conductivity.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Which of the following materials is used to make a semiconductor?
  • Sulphur
  • Correct Answer
    Silicon
  • Tantalum
  • Copper

The most basic semiconductor materials are silicon and germanium. Atoms in metallic elements hold their peripheral electrons loosely, such materials make good conductors. Peripheral electrons in non-metallic elements are tightly bound, such materials are insulators. Germanium and silicon fall somewhere between the two categories but are mostly insulators when pure. Doping with impurities increases their conductivity.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Substances such as silicon in a pure state are usually good:
  • conductors
  • tuned circuits
  • inductors
  • Correct Answer
    insulators

The most basic semiconductor materials are silicon and germanium. Atoms in metallic elements hold their peripheral electrons loosely, such materials make good conductors. Peripheral electrons in non-metallic elements are tightly bound, such materials are insulators. Germanium and silicon fall somewhere between the two categories but are mostly insulators when pure. Doping with impurities increases their conductivity.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

A semiconductor is said to be doped when it has added to it small quantities of:
  • ions
  • electrons
  • Correct Answer
    impurities
  • protons

Pure germanium and silicon are doped with impurities to produce the basic semiconductor materials. Certain doping impurities add free electrons, forming N-Type material while others accept electrons, thus creating 'holes' found in P-Type material.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What is the principal characteristic of a Zener diode?
  • A negative resistance region
  • An internal capacitance that varies with the applied voltage
  • Correct Answer
    A constant voltage under conditions of varying current
  • A constant current under conditions of varying voltage

Zener diodes maintain a constant voltage across a range of currents. The Varactor (or Varicap) is a diode used under reverse bias as a "voltage-variable capacitor". Hot-carrier (or Schottky-barrier) diodes have lower forward voltage and good high-frequency response: their speed make them useful in Very High Frequency mixers or detectors; in power circuits, they are excellent rectifiers in switching power supplies. PIN diodes (with a layer of undoped or lightly doped 'intrinsic' silicon between the P and N regions) are used as switches or attenuators.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What type of semiconductor diode varies its internal capacitance as the voltage applied to its terminals varies?
  • Silicon-controlled rectifier
  • Hot-carrier (Schottky)
  • Correct Answer
    Varactor
  • Zener

Zener diodes maintain a constant voltage across a range of currents. The Varactor (or Varicap) is a diode used under reverse bias as a "voltage-variable capacitor". Hot-carrier (or Schottky-barrier) diodes have lower forward voltage and good high-frequency response: their speed make them useful in Very High Frequency mixers or detectors; in power circuits, they are excellent rectifiers in switching power supplies. PIN diodes (with a layer of undoped or lightly doped 'intrinsic' silicon between the P and N regions) are used as switches or attenuators.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What is a common use for the hot-carrier (Schottky) diode?
  • As balanced mixers in FM generation
  • As a variable capacitance in an automatic frequency control (AFC) circuit
  • As a constant voltage reference in a power supply
  • Correct Answer
    As VHF and UHF mixers and detectors

Zener diodes maintain a constant voltage across a range of currents. The Varactor (or Varicap) is a diode used under reverse bias as a "voltage-variable capacitor". Hot-carrier (or Schottky-barrier) diodes have lower forward voltage and good high-frequency response: their speed make them useful in Very High Frequency mixers or detectors; in power circuits, they are excellent rectifiers in switching power supplies. PIN diodes (with a layer of undoped or lightly doped 'intrinsic' silicon between the P and N regions) are used as switches or attenuators.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What limits the maximum forward current in a junction diode?
  • Back EMF
  • Peak inverse voltage
  • Correct Answer
    Junction temperature
  • Forward voltage

Diodes conduct in one direction only: under forward bias, maximum forward current is limited by acceptable junction temperature. The voltage drop across the junction (volts) multiplied by the forward current (amperes) gives rise to heat dissipation (watts). Surviving a reverse bias is determined by the Peak Inverse Voltage (PIV) rating.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What are the major ratings for junction diodes?
  • Maximum reverse current and capacitance
  • Maximum forward current and capacitance
  • Maximum reverse current and peak inverse voltage (PIV)
  • Correct Answer
    Maximum forward current and peak inverse voltage (PIV)

Diodes conduct in one direction only: under forward bias, maximum forward current is limited by acceptable junction temperature. The voltage drop across the junction (volts) multiplied by the forward current (amperes) gives rise to heat dissipation (watts). Surviving a reverse bias is determined by the Peak Inverse Voltage (PIV) rating.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Structurally, what are the two main categories of semiconductor diodes?
  • Correct Answer
    Junction and point contact
  • Vacuum and point contact
  • Electrolytic and point contact
  • Electrolytic and junction

Point-contact diodes, where a small metal whisker touches the semiconductor material, exhibit low capacitance and serve as RF detectors or UHF mixers. Junction diodes are formed with adjacent blocks of P and N material; these are usable from DC to microwave.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What is a common use for point contact diodes?
  • As a constant current source
  • As a constant voltage source
  • As a high voltage rectifier
  • Correct Answer
    As an RF detector

Point-contact diodes, where a small metal whisker touches the semiconductor material, exhibit low capacitance and serve as RF detectors or UHF mixers. Junction diodes are formed with adjacent blocks of P and N material; these are usable from DC to microwave.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What is one common use for PIN diodes?
  • As a constant current source
  • As a high voltage rectifier
  • As a constant voltage source
  • Correct Answer
    As an RF switch

Zener diodes maintain a constant voltage across a range of currents. The Varactor (or Varicap) is a diode used under reverse bias as a "voltage-variable capacitor". Hot-carrier (or Schottky-barrier) diodes have lower forward voltage and good high-frequency response: their speed make them useful in Very High Frequency mixers or detectors; in power circuits, they are excellent rectifiers in switching power supplies. PIN diodes (with a layer of undoped or lightly doped 'intrinsic' silicon between the P and N regions) are used as switches or attenuators.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

A Zener diode is a device used to:
  • dissipate voltage
  • decrease current
  • increase current
  • Correct Answer
    regulate voltage

Zener diodes maintain a constant voltage across a range of currents. The Varactor (or Varicap) is a diode used under reverse bias as a "voltage-variable capacitor". Hot-carrier (or Schottky-barrier) diodes have lower forward voltage and good high-frequency response: their speed make them useful in Very High Frequency mixers or detectors; in power circuits, they are excellent rectifiers in switching power supplies. PIN diodes (with a layer of undoped or lightly doped 'intrinsic' silicon between the P and N regions) are used as switches or attenuators.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

If a Zener diode rated at 10 V and 50 watts was operated at maximum dissipation rating, it would conduct ____ amperes:
  • 50
  • 0.05
  • 0.5
  • Correct Answer
    5

P = E times I. Watts = volts times amperes. Thus, I = P divided by E: 50 watts divided by 10 volts = 5 amperes.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

The power-handling capability of most Zener diodes is rated at 25 degrees C or approximately room temperature. If the temperature is increased, the power handling capability is:
  • much greater
  • slightly greater
  • Correct Answer
    less
  • the same

Heat flows from hot to cold. If ambient temperature is higher, less heat can be drained from the junction, the junction will reach maximum safe operating temperature quicker.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What is the alpha of a bipolar transistor?
  • The change of base current with respect to collector current
  • The change of collector current with respect to gate current
  • Correct Answer
    The change of collector current with respect to emitter current
  • The change of collector current with respect to base current

In a 'common base' configuration where the Emitter is the input and the Collector is the output, the Alpha factor (or common base forward current transfer ratio) is a ratio of a change in Collector current to the corresponding change in Emitter current. In a 'common emitter' configuration where the Base is the input and the Collector is the output, the Beta factor (or common emitter forward current gain) is a ratio of a change in Collector current to a given change in Base current. The Beta factor applies equally to a Common Collector configuration where the Base is also the input.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What is the beta of a bipolar transistor?
  • The change of collector current with respect to emitter current
  • The change of base current with respect to gate current
  • Correct Answer
    The change of collector current with respect to base current
  • The change of base current with respect to emitter current

In a 'common base' configuration where the Emitter is the input and the Collector is the output, the Alpha factor (or common base forward current transfer ratio) is a ratio of a change in Collector current to the corresponding change in Emitter current. In a 'common emitter' configuration where the Base is the input and the Collector is the output, the Beta factor (or common emitter forward current gain) is a ratio of a change in Collector current to a given change in Base current. The Beta factor applies equally to a Common Collector configuration where the Base is also the input.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Which component conducts electricity from a negative emitter to a positive collector when its base voltage is made positive?
  • A varactor
  • A triode vacuum tube
  • A PNP transistor
  • Correct Answer
    An NPN transistor

The terms Emitter, Collector and Base refer to bipolar transistors, of which there are two types: NPN and PNP. The Base-Emitter junction must be forward-biased for Base current to exist. A positive voltage on the Base supposes P material for conduction to take place, the 'sandwich' is thus NPN. Inversely, a negative Base voltage relates to a PNP.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What is the alpha of a bipolar transistor in common base configuration?
  • Correct Answer
    Forward current gain
  • Forward voltage gain
  • Reverse current gain
  • Reverse voltage gain

The Alpha being a number smaller than 1, many authors refer to it as the "common base forward current transfer ratio" rather than a gain. In a 'common base' configuration where the Emitter is the input and the Collector is the output, the Alpha factor (or common base forward current transfer ratio) is a ratio of a change in Collector current to the corresponding change in Emitter current. In a 'common emitter' configuration where the Base is the input and the Collector is the output, the Beta factor (or common emitter forward current gain) is a ratio of a change in Collector current to a given change in Base current. The Beta factor applies equally to a Common Collector configuration where the Base is also the input.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In a bipolar transistor, the change of collector current with respect to base current is called:
  • delta
  • alpha
  • Correct Answer
    beta
  • gamma

In a 'common base' configuration where the Emitter is the input and the Collector is the output, the Alpha factor (or common base forward current transfer ratio) is a ratio of a change in Collector current to the corresponding change in Emitter current. In a 'common emitter' configuration where the Base is the input and the Collector is the output, the Beta factor (or common emitter forward current gain) is a ratio of a change in Collector current to a given change in Base current. The Beta factor applies equally to a Common Collector configuration where the Base is also the input.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

The alpha of a bipolar transistor is specified for what configuration?
  • Common collector
  • Common gate
  • Common emitter
  • Correct Answer
    Common base

In a 'common base' configuration where the Emitter is the input and the Collector is the output, the Alpha factor (or common base forward current transfer ratio) is a ratio of a change in Collector current to the corresponding change in Emitter current. In a 'common emitter' configuration where the Base is the input and the Collector is the output, the Beta factor (or common emitter forward current gain) is a ratio of a change in Collector current to a given change in Base current. The Beta factor applies equally to a Common Collector configuration where the Base is also the input.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

The beta of a bipolar transistor is specified for what configurations?
  • Correct Answer
    Common emitter or common collector
  • Common emitter or common gate
  • Common base or common collector
  • Common base or common emitter

In a 'common base' configuration where the Emitter is the input and the Collector is the output, the Alpha factor (or common base forward current transfer ratio) is a ratio of a change in Collector current to the corresponding change in Emitter current. In a 'common emitter' configuration where the Base is the input and the Collector is the output, the Beta factor (or common emitter forward current gain) is a ratio of a change in Collector current to a given change in Base current. The Beta factor applies equally to a Common Collector configuration where the Base is also the input.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Which component conducts electricity from a positive emitter to a negative collector when its base is made negative?
  • A varactor
  • An NPN transistor
  • Correct Answer
    A PNP transistor
  • A triode vacuum tube

The terms Emitter, Collector and Base refer to bipolar transistors, of which there are two types: NPN and PNP. The Base-Emitter junction must be forward-biased for Base current to exist. A positive voltage on the Base supposes P material for conduction to take place, the 'sandwich' is thus NPN. Inversely, a negative Base voltage relates to a PNP.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Alpha of a bipolar transistor is equal to:
  • beta / (1 - beta)
  • Correct Answer
    beta / (1 + beta)
  • beta x (1 + beta)
  • beta x (1 - beta)

Alpha ('common base') is always a number lesser than 1 ( the Emitter current is necessarily larger than the Collector current because the Base current also flows through the Emitter ). Beta ('common emitter') is normally a number greater than 10 ( the Collector current is always several times the Base current ). The Alpha is equal to Beta divided by 1 plus Beta. The Beta is equal to Alpha divided by 1 minus Alpha.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

The current gain of a bipolar transistor in common emitter or common collector compared to common base configuration is:
  • usually about half
  • Correct Answer
    high to very high
  • very low
  • usually about double

Alpha ('common base') is always a number lesser than 1 ( the Emitter current is necessarily larger than the Collector current because the Base current also flows through the Emitter ). Beta ('common emitter') is normally a number greater than 10 ( the Collector current is always several times the Base current ). The Alpha is equal to Beta divided by 1 plus Beta. The Beta is equal to Alpha divided by 1 minus Alpha.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Beta of a bipolar transistor is equal to:
  • alpha x (1 - alpha)
  • alpha x (1 + alpha)
  • Correct Answer
    alpha / (1 - alpha)
  • alpha / (1 + alpha)

Alpha ('common base') is always a number lesser than 1 ( the Emitter current is necessarily larger than the Collector current because the Base current also flows through the Emitter ). Beta ('common emitter') is normally a number greater than 10 ( the Collector current is always several times the Base current ). The Alpha is equal to Beta divided by 1 plus Beta. The Beta is equal to Alpha divided by 1 minus Alpha.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What is an enhancement-mode FET?
  • Correct Answer
    An FET without a channel; no current occurs with zero gate voltage
  • An FET with a channel that blocks voltage through the gate
  • An FET with a channel that allows current when the gate voltage is zero
  • An FET without a channel to hinder current through the gate

An Enhancement-mode Insulated Gate Field Effect Transistor (IGFET) is constructed without a channel. There is no Drain current with zero Gate voltage. A voltage applied to the gate leads to the creation of a channel. A forward bias on the gate heightens the concentration of charge carriers which, in turn, 'enhances' conduction. A Depletion-mode Insulated Gate Field Effect Transistor has a channel. Drain current is possible even without a Gate voltage. A reverse bias on the Gate depletes charge carriers in the channel, thus reducing Drain current. A forward bias on the Gate can make the channel even more conductive.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What is a depletion-mode FET?
  • An FET that has a channel that blocks current when the gate voltage is zero
  • Correct Answer
    An FET that has a channel with no gate voltage applied; a current flows with zero gate voltage
  • An FET without a channel; no current flows with zero gate voltage
  • An FET without a channel to hinder current through the gate

An Enhancement-mode Insulated Gate Field Effect Transistor (IGFET) is constructed without a channel. There is no Drain current with zero Gate voltage. A voltage applied to the gate leads to the creation of a channel. A forward bias on the gate heightens the concentration of charge carriers which, in turn, 'enhances' conduction. A Depletion-mode Insulated Gate Field Effect Transistor has a channel. Drain current is possible even without a Gate voltage. A reverse bias on the Gate depletes charge carriers in the channel, thus reducing Drain current. A forward bias on the Gate can make the channel even more conductive.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Why do many MOSFET devices have built-in gate protective Zener diodes?
  • The gate-protective Zener diode provides a voltage reference to provide the correct amount of reverse-bias gate voltage
  • Correct Answer
    The gate-protective Zener diode prevents the gate insulation from being punctured by small static charges or excessive voltages
  • The gate-protective Zener diode keeps the gate voltage within specifications to prevent the device from overheating
  • The gate-protective Zener diode protects the substrate from excessive voltages

The Gate in an Insulated Gate Field Effect Transistor (IGFET or metal-oxide-semiconductor FET, MOSFET) is insulated from the channel by a thin oxide layer. Static electricity or excessive voltage can easily destroy the dielectric layer.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Why are special precautions necessary in handling FET and CMOS devices?
  • They are light-sensitive
  • They have micro-welded semiconductor junctions that are susceptible to breakage
  • They have fragile leads that may break off
  • Correct Answer
    They are susceptible to damage from static charges

The Gate in an Insulated Gate Field Effect Transistor (IGFET or metal-oxide-semiconductor FET, MOSFET) is insulated from the channel by a thin oxide layer. Static electricity or excessive voltage can easily destroy the dielectric layer.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

How does the input impedance of a field-effect transistor (FET) compare with that of a bipolar transistor?
  • Correct Answer
    An FET has high input impedance; a bipolar transistor has low input impedance
  • One cannot compare input impedance without knowing supply voltage
  • An FET has low input impedance; a bipolar transistor has high input impedance
  • The input impedance of FETs and bipolar transistors is the same

Bipolar transistors are operated with a forward-biased (conductive) Base-Emitter junction. Bipolar transistors are current amplifiers. Impedance, as a ratio of voltage to current, is necessarily low when voltage is low and current is high. The Field Effect Transistor, with a reverse biased Gate to channel junction, and the Insulated Gate Field Effect Transistor (IGFET or metal-oxide-semiconductor FET, MOSFET) with a Gate separated from the channel by a dielectric, are high impedance devices.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What are the three terminals of a junction field-effect transistor (JFET)?
  • Gate 1, gate 2, drain
  • Correct Answer
    Gate, drain, source
  • Emitter, base 1, base 2
  • Emitter, base, collector

Remember your Basic Qualification? The FET comprises a Source, a Gate and a Drain. They come in two types: N-Channel and P-Channel.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What are the two basic types of junction field-effect transistors (JFET)?
  • Correct Answer
    N-channel and P-channel
  • High power and low power
  • MOSFET and GaAsFET
  • Silicon and germanium

Remember your Basic Qualification? The FET comprises a Source, a Gate and a Drain. They come in two types: N-Channel and P-Channel.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Electron conduction in an n-channel depletion type MOSFET is associated with:
  • p-channel depletion
  • p-channel enhancement
  • q-channel enhancement
  • Correct Answer
    n-channel depletion

This seems too simple to be true, the words in the question give the answer away.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Electron conduction in an n-channel enhancement MOSFET is associated with:
  • q-channel depletion
  • p-channel enhancement
  • p-channel depletion
  • Correct Answer
    n-channel enhancement

This seems too simple to be true, the words in the question give the answer away.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Hole conduction in a p-channel depletion type MOSFET is associated with:
  • Correct Answer
    p-channel depletion
  • n-channel enhancement
  • q-channel depletion
  • n-channel depletion

This seems too simple to be true, the words in the question give the answer away.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Hole conduction in a p-channel enhancement type MOSFET is associated with:
  • n-channel depletion
  • n-channel enhancement
  • q-channel depletion
  • Correct Answer
    p-channel enhancement

This seems too simple to be true, the words in the question give the answer away.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What are the three terminals of a silicon controlled rectifier (SCR)?
  • Gate, base 1 and base 2
  • Base, collector and emitter
  • Gate, source and sink
  • Correct Answer
    Anode, cathode and gate

The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN. It comprises three electrodes: Anode, Gate and Cathode. As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material. Without gate current, the SCR looks like a regular non-conducting junction diode. Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode. Conduction continues unless current falls below a critical level. One typical application is an overvoltage protection circuit in a power supply.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

What are the two stable operating conditions of a silicon controlled rectifier (SCR)?
  • NPN conduction and PNP conduction
  • Oscillating and quiescent
  • Correct Answer
    Conducting and non-conducting
  • Forward conducting and reverse conducting

The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN. It comprises three electrodes: Anode, Gate and Cathode. As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material. Without gate current, the SCR looks like a regular non-conducting junction diode. Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode. Conduction continues unless current falls below a critical level. One typical application is an overvoltage protection circuit in a power supply.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

When a silicon controlled rectifier (SCR) is triggered, to what other semiconductor diode are its electrical characteristics similar (as measured between its cathode and anode)?
  • The PIN diode
  • The hot-carrier (Schottky) diode
  • The varactor diode
  • Correct Answer
    The junction diode

The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN. It comprises three electrodes: Anode, Gate and Cathode. As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material. Without gate current, the SCR looks like a regular non-conducting junction diode. Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode. Conduction continues unless current falls below a critical level. One typical application is an overvoltage protection circuit in a power supply.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Under what operating condition does a silicon controlled rectifier (SCR) exhibit electrical characteristics similar to a forward-biased silicon rectifier?
  • When it is used as a detector
  • During a switching transition
  • Correct Answer
    When it is gated "on"
  • When it is gated "off"

The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN. It comprises three electrodes: Anode, Gate and Cathode. As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material. Without gate current, the SCR looks like a regular non-conducting junction diode. Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode. Conduction continues unless current falls below a critical level. One typical application is an overvoltage protection circuit in a power supply.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

The silicon controlled rectifier (SCR) is what type of device?
  • NPPN
  • PNNP
  • PPNN
  • Correct Answer
    PNPN

The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN. It comprises three electrodes: Anode, Gate and Cathode. As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material. Without gate current, the SCR looks like a regular non-conducting junction diode. Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode. Conduction continues unless current falls below a critical level. One typical application is an overvoltage protection circuit in a power supply.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

The control element in the silicon controlled rectifier (SCR) is called the:
  • emitter
  • Correct Answer
    gate
  • anode
  • cathode

The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN. It comprises three electrodes: Anode, Gate and Cathode. As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material. Without gate current, the SCR looks like a regular non-conducting junction diode. Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode. Conduction continues unless current falls below a critical level. One typical application is an overvoltage protection circuit in a power supply.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

The silicon controlled rectifier (SCR) is a member of which family?
  • Phase locked loops
  • Varactors
  • Varistors
  • Correct Answer
    Thyristors

The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN. It comprises three electrodes: Anode, Gate and Cathode. As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material. Without gate current, the SCR looks like a regular non-conducting junction diode. Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode. Conduction continues unless current falls below a critical level. One typical application is an overvoltage protection circuit in a power supply.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

In amateur radio equipment, which is the major application for the silicon controlled rectifier (SCR)?
  • Microphone preamplifier circuit
  • SWR detector circuit
  • Correct Answer
    Power supply overvoltage "crowbar" circuit
  • Class C amplifier circuit

The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN. It comprises three electrodes: Anode, Gate and Cathode. As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material. Without gate current, the SCR looks like a regular non-conducting junction diode. Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode. Conduction continues unless current falls below a critical level. One typical application is an overvoltage protection circuit in a power supply.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Which of the following devices has anode, cathode, and gate?
  • Correct Answer
    The silicon controlled rectifier (SCR)
  • The bipolar transistor
  • The field effect transistor
  • The triode vacuum tube

The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN. It comprises three electrodes: Anode, Gate and Cathode. As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material. Without gate current, the SCR looks like a regular non-conducting junction diode. Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode. Conduction continues unless current falls below a critical level. One typical application is an overvoltage protection circuit in a power supply.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

When it is gated "on", the silicon controlled rectifier (SCR) exhibits electrical characteristics similar to a:
  • reverse-biased silicon rectifier
  • forward-biased PIN diode
  • reverse-biased hot-carrier (Schottky) diode
  • Correct Answer
    forward-biased silicon rectifier

The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN. It comprises three electrodes: Anode, Gate and Cathode. As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material. Without gate current, the SCR looks like a regular non-conducting junction diode. Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode. Conduction continues unless current falls below a critical level. One typical application is an overvoltage protection circuit in a power supply.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Which of the following is a PNPN device?
  • Zener diode
  • Correct Answer
    Silicon controlled rectifier (SCR)
  • PIN diode
  • Hot carrier (Schottky) diode

The SCR, part of the Thyristor family, is made of four layers of alternating P and N type material, namely PNPN. It comprises three electrodes: Anode, Gate and Cathode. As can be expected, the two outermost electrodes, the Anode and the Cathode are respectively type P and type N material. Without gate current, the SCR looks like a regular non-conducting junction diode. Once triggered via the Gate, the SCR resembles a forward-biased (conducting) junction diode. Conduction continues unless current falls below a critical level. One typical application is an overvoltage protection circuit in a power supply.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

Tags: none

Go to L02 Go to L05