Module 4 Flashcards
What are the most important elements used for semiconductors
Silicone, germanium, selenium and copper oxide
What is doping
Moving electrons and holes
What is known about p type material
Number of electrons trapped is lower resulting in more holes
How is a single crystal semiconductor diode made
By doping two semiconductor p-n crystals together
Does a semiconductor diode block current or let it through
It can do either
How much voltage is required to break down the depletion zone in a silicone diode
0.7V
What is the threshold voltage
A voltage above the depletion zone voltage
What semiconductor diode is reverse biased current leakage the greatest
Germanium diodes
What is the maximum forward current
Quite literally the maximum forward current allowed to flow through the device
What happens If IFMAX is exceeded
More heat will be generated and could result in destruction
What is recommended if running diodes close to current capacity
Provide additional cooling
What are the 3 types of semiconductor diodes
Microdiodes, rectifier diodes and heavy current diodes.
What is diffusion voltage in germanium
0.3v
What is the diffusion voltage in silicon
0.7v
Charge displacement cannot be used where
Batteries
What is a fundamental semiconductor diode
A p-n diode
Can a semiconductor diode block current or let it through
It can block current or let it through
What is described as a type of valve for electrical current
A semiconductor diode
Where would you find microdiodes mainly used
In communication technology
Where would you see rectifier diodes
Electrical power supply devises
Where would heavy current diodes be used
Rectifier circuits for large loads
What type of diodes can be used to protect against back EMF
Freewheeling diodes
When diodes are connected in series what will the forward current be
The same as the current going in
When diodes are connected in parallel what happens to the current
It’s divided between the diodes
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
6
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
4
How many junctions does a thyristor have
3
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
AC
How many layers does a bi polar transistor have
3
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
3
What does SCR stand for
Silicon Controlled Rectifier
What is
