D6 DIODES Flashcards
The diode is a (linear/non-linear) device:
non-linear
A diode in reverse breakdown can be used as a
voltage regulator or voltage reference
As long as a Zener diode is in reverse breakdown, an approximately ____ voltage called ____ will be found across a parallel load
constant, Vz
If the current through a Zener diode in breakdown is less than zero, then
the diode no longer controls the voltage across itself and therefore, any parallel loads
True/False: The Zener diode has a non-zero Zener resistance, Rz
True
In a pn junction diode, the point where the semiconductor material changes from p to n type is called the
metallurgical junction
The pn junction diode is constructed using the impurity process called _____
doping
The p-type region of a diode is also called the
anode (the arrow) +
The n-type region of a diode is also called the
cathode (the line) -
In a Conventional diode the + charge moves
the + charge moves in the direction opposite to current (electron flow)
which is positive anode or cathode
the cathode attracts + charge. The anode attracts negative charge.
Zener diodes are designed to operate in
reverse = Zener voltage otherwise in forward bias they drop only 0.7 volts
Which transistor has the arrow of the emitter poiNting towards the base (PNP/NPN)
PNP
How can one spot is the Bias is forward or reversed?
Negative to Positive is forwards
Positive to Positive is reversed
Compare to battery and resistors in circuit
What makes silicon more desirable to use than germanium?
Silicon has more resistance to heat than germanium.
What happens with a negative temperature coefficient?
Negative temperature coefficient means increase temperature=decrease in resistance.
What are the two semiconductor elements suitable for electronic applications?
Silicon (Si) 0.7 VD and Germanium (Ge) 0.3 VD
Crystal lattice structure is part of what?
Covalent bonding where 8 electrons are shared = a stable 8 electron arrangement
Pentavalent is what type of impurity
N-type, pure semiconductor crystal with 5 electrons, CATHODE
Trivalent is what type of impurity
P- type with 3 electrons and a semiconductor crystal, ANODE
As temperature of a material increases it electrical resistance decreases
Negative Temperature Coefficient
Silicon has__________resistance than germanium at room temperature
1000 times more
Semiconductor materials .
Have characteristics that fall between insulators and conductors
When using semiconductors, what is the major problem that must be controlled?
Heat and the changes caused by heat.
Holes constantly drift towards
drift towards the NEGATIVE terminal of the voltage source.
Electrons always flow
towards the POSITIVE terminal of the voltage source
What are 2 pentavalent impurities?
Arsenic & Antimony
What are 2 trivalent impurites?
Indium & Gallium
Electrons in the outer band or shell of an element are characterized by their:
Energy
The conductivity of P-type and N-type semiconductor materials depends on:
the doping level.
A forward biased PN-junction conducts a current when:
a negative voltage source is connected to N-material.
A forward biased PN-junction requires:
a negative voltage source connected to N-material.
The reverse bias condition causes the barrier voltage to seemingly:
increase in level. unless it is a Zener diode
A zener diode’s maximum current rating is determined principally by its:
maximum power dissipation.
Zener diodes are used in two different ways to control voltage; these are called:
line or input and load regulation.
In a zener diode, the cathode is:
a Z shaped bar.
indicated by a color band.
reverse biased.
In testing a zener diode with a Digital Multimeter, what tests can be performed:
a continuity test.
reverse resistance test.
forward resistance test.
In testing a diode with a Digital Multimeter, what tests can be performed:
continuity test.
reverse resistance test. (Infinity resistance)
forward resistance test. (low resistance)
Dissipation of heat due to I^2R Loss with diodes and transistors are resolved by the use of
Heat sinks
what acts as an acr suppressor, prevents insulation failure in windings and reduces heavy arcing
Freewheeling diodes
- Mathematically gives the load (parallel resistor) what it requires to remain balanced.
What has a Reverse BIas
As brightness increases, current increases and is amplified by a transistor.
Photodiode image: arrow(s) pointing towards the anode/cathode >l
What is Forward Bias
Voltage control during doping produces colour
LED image: arrow(s) pointing away l<
Red = less voltage
Amber = med voltage
Green = most voltage
NPN and PNP are classed as what type of transistors
Bipolar- junction transistor
The three parts or regions of a transistor are called:
emitter, base, collector.
In order to perform voltage regulation using a zener diode, what other circuit component is required:
a series resistor
