Module 4 Flashcards by Richard Fry

What are the most important elements used for semiconductors

Silicone, germanium, selenium and copper oxide

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What is doping

Moving electrons and holes

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What is known about p type material

Number of electrons trapped is lower resulting in more holes

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How is a single crystal semiconductor diode made

By doping two semiconductor p-n crystals together

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Does a semiconductor diode block current or let it through

It can do either

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How much voltage is required to break down the depletion zone in a silicone diode

0.7V

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What is the threshold voltage

A voltage above the depletion zone voltage

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What semiconductor diode is reverse biased current leakage the greatest

Germanium diodes

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What is the maximum forward current

Quite literally the maximum forward current allowed to flow through the device

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What happens If IFMAX is exceeded

More heat will be generated and could result in destruction

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What is recommended if running diodes close to current capacity

Provide additional cooling

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What are the 3 types of semiconductor diodes

Microdiodes, rectifier diodes and heavy current diodes.

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What is diffusion voltage in germanium

0.3v

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What is the diffusion voltage in silicon

0.7v

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Charge displacement cannot be used where

Batteries

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What is a fundamental semiconductor diode

A p-n diode

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Can a semiconductor diode block current or let it through

It can block current or let it through

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What is described as a type of valve for electrical current

A semiconductor diode

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Where would you find microdiodes mainly used

In communication technology

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Where would you see rectifier diodes

Electrical power supply devises

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Where would heavy current diodes be used

Rectifier circuits for large loads

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What type of diodes can be used to protect against back EMF

Freewheeling diodes

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When diodes are connected in series what will the forward current be

The same as the current going in

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When diodes are connected in parallel what happens to the current

It’s divided between the diodes

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What will happen if a diode is wired in a reverse bias direction

Very high resistance or short circuit

What will a diode show if wired in bias direction

Very low resistance

What can diodes resistance be measured with

A multimeter

When a multimeter is set to the testing diode setting how much voltage will be supplied

2.5-3.5v

What will a serviceable diodes voltage show on a multimeter when tested in the forward bias direction

0.6- 0.7v

What will a multimeter show when a diode is tested in the reverse bias direction

Overload OL

How can you tell If a diode has failed OPEN circuit

It will indicate overload or OL on a multimeter in both forward bias and reverse bias

What will happen when a diode has failed SHORT circuit

It will show 0 in both directions and an audible beep is heard

What is the angle of opening in a diode charging

30 to 60 degrees

What are the two things a semiconductor diode can do to current

Block it or let it through

How are P and N type materials created

Doping

What is the area between P and N type materials called

Depletion later

In reverse biased config does a diode block or conduct

Blocks

What is the voltage that breaks through a depletion zone in fwd bias condition called

Threshold voltage

What are the threshold voltages for silicon and germanium

Germanium 0.3 Silicon 0.7

Do diodes block completely in reverse bias

No depends on semiconductor type

What is residual reverse biased current also known as

Current caused by impurities in the Chrystal

Which diode has a higher breakdown voltage silicone or germanium

Silicon

What temp can silicon and germanium withstand

Silicon 180 degrees c Germanium 80 degrees c

When testing a diode with a multimeter what voltage would you expect in the forward and reverse bias directions if the diode was serviceable

Fwd 0.7v Rev batt volt assume si

How many diodes are required for a single wave rectifier

One

In a 3 phase rectifier how many diodes are required

What is the advantage of a bridge rectifier over a full wave rectifier

Does not need a transformer

How is the zenner diode normally connected

In the reverse biased direction

What is the zenner diode typically used for

Voltage regulation

What is the effect called when a reverse biased zenner diode suddenly starts conducting

The zenner effect

What is the optimum voltage for a zenner diode and why

Breakdown voltage between 5 and 7v this means the dynamic resistance is especially small

What determines the operating voltage of a zenner diode

The amount of dopant

What determines the light colour from an LED

Depends on the semiconductor material used

What is the lifespan of an LED

6 to 11 Years

What is the relationship between light and resistance of a LDR

Increased light - decreased resistance

What are the resistance characteristics of PTCs

Temp increase resistance increase

What are the characteristics of NTCs

Temp increase resistance decrease

What is the temperature at which the resistance of a PTC sudden you increases called

Reference temperature

What are VDRs used for

Protect systems against high voltage

How many P N layers does a thyristor have

How many junctions does a thyristor have

When does a thyristor conduct

When zero sweep voltage is exceeded

With no voltage at the gate what is the voltage called that makes a thyristor suddenly conduct

Zero sweep voltage

How is a thyristor turned off

Switch the circuit off completely

What sort of current does a thyristor control

High current

What sort of current does a triad control

How many layers does a bi polar transistor have

What are the 3 terminals of a transistor called

Base Collector Emitter

Between which terminals is a transistor controlled

Base/emitter

In which devices can integrated circuits be found. Alalouge digital or both

Both

Which components can be found in ICs

Transistors Capacitors Resistors

What are the benefits of ICs

Small Cheap Low power consumption

What are the disadvantages of ICs

Heat Difficult to maintain

What does LDR stand for

Light Dependant Resistor

What does VDR stand for

Voltage Dependent Resistor

What is a thyristor diode

A four layer diode consisting of four semiconductor zones with an anode terminal and a cathode terminal

How many P N junctions are there in a thyristor

What does SCR stand for

Silicon Controlled Rectifier

What is