Electronics Flashcards
How many electrons are in the outer shell?
8
What are covalent bonds?
Chemical bond of sharing electron pairs between atoms
What are valence electrons?
Electrons in the outer shell that can be shared with other atoms to form covalent bonds
How many electrons do the best conductors have in their outer shell?
1-3
How many electrons do the best insulators have in their outer shell?
5-8
How many valence electrons do semi conductors have?
4
What is doping?
Process of adding small impurity to semiconductor to make N type or P type
What is an N type seni conductor?
Has a material with 5 valence electrons introduced to it, outer 4 valence electrons create covalent bond leaving one extra electron to move around freely. There is an excess of Negative electrons hence the N.
What is a P type semi conductor?
A material with 3 valence electrons is introduced to a semi conductor, the outer valence electrons create a covalent bond with the 3 valence electrons of the new material leaving one hole available. This makes this semi conductor more Positive, hence the P
What is negative temperature coefficient
As temperature increases, resistance decreases, current increases.
What is built into diodes to dissipate heat?
Heat sink fans
What is a diode made of?
A P type and an N type semiconductor
What is the name and polarity of the P type semi conductor?
Anode, positive.
What is the name and polarity of the N type semi conductor?
Cathode, negative
Voltage drop across reverse and forward bias diodes
Reverse: will read source, acts as an open
Forward: silicon: 0.7V, Germanium: 0.3V
Resistance of reverse and forward bias diodes
Reverse: infinite, will not conduct
Forward: zero, will conduct easily with very little voltage drop
What type of switch is a diode?
Solid state switch
When does breakdown voltage occur?
When PIV is surpassed
What is PIV?
Peak inverse voltage. Max voltage diode can safely block. If value is passed the diode will start to conduct very high current and destroy itself (breakdown voltage)
Forward Current Rating:
Max RMS current value that diode can safely handle without damage.
Zener diodes conduct in reverse or forward bias?
Forward.
Why are Zener diodes used as voltage regulators?
In reverse bias they are able to change their resistance to maintain constant voltage over a range of currents.
What are zener diodes rated in?
Watts
Term for turning AC into DC
Rectifier
Term for turning DC into AC
Inverter
Formula for finding Eavg on a half wave circuit
Epeak / pi
Formula for finding Eavg on a full wave
Epeak • 2 / pi
Formula for finding Iavg on half wave
Ipeak / pi
Formula for finding Iavg on full wave
Ipeak • 2 / pi
Formula for finding power on a half wave
Epeak • Ipeak / 4
Or
ERMS • IRMS / 2
Formula for finding power on a full wave
Epeak • Ipeak / 2
Or
ERMS • IRMS
What is a rectifier half wave?
Only one alternation is allowed through, diode blocks the other alternation.
What amount of power is produced in a half wave?
Half the source power, half the waveform is blocked.
Dc meters measure ______ values
Average
AC meters measure ________ values
rMS
What is a rectifier full wave?
Both alternations of the sine wave are allowed through, but the negative has turned to positive, both waves are always positive
Which is more advantages, half or full wave? Why?
Full wave DC, both alternations are used, more power dissipated
Name two types of full wave rectifiers
Bridge, biphase
In a bridge rectifier, load power =
Same power as source.
What would happen in a bridge rectifier if one of the diodes was open?
Would change from a full wave to a half wave because you would lose one of the pulses.
What would happen in a bridge rectifier if one of the diodes was incorrect polarity?
Short circuit.
What is PIV on a biphase rectifier?
Peak of voltage across both coils.
What is the purpose of capacitors for filtering?
To smooth out the pulses.
What must the PIV be rated in a filtering circuit?
2x the peak value, capacitor acts as source so there is no down in the waveform
How is a capacitor connected in a circuit?
In series with a diode.
What does Max filtering mean?
DC avg = AC peak
What are the bridge rectifier colour codes
Red: positive output of load
Black: negative output of load
Yellow: ac input
PIV in a half wave filtering circuit would be
2x the peak without filtering.
What is DCWV in a biphase rectifier?
Peak voltage on one winding
As the base of a NPN becomes more positive, the collector current _____
Increases
Collector current in a PNP will decrease as base becomes less
Negative
When a transistor is fully on, the voltage across ce is
0.1V
When a transistor is fully on the voltage across be is
0.7V
When a transistor is saturated, the impedence between ce is low or high?
Low
The beta can range anywhere from ____ to _____
10 to 500
What determines if an element is classified as conductor, insulator, or semiconductor?
The number of valence electrons
What type of atoms are used for doping n type and p type semiconductors?
N type: pentavalent
P type: trivalent
What is meant by forward bias?
Connected polarity which will allow diode to conduct. (Positive to anode, negative to cathode)
What is meant by reverse bias?
Connected polarity which will make diode block
What kind of resistance would you expect when checking a diode with an on meter?
Forward bias: low resistance
Reverse bias: high resistance
What type of connection is a free wheeling diode made in?
Reverse bias diode in parallel
Describe the valence shell of a P type
Covalent bonds with an atom with three electrons, leaving excess of one hole making it more positive
Describe the valence shell of an N type
Covalent bonds with an atom with an excess of negative electrons, leaving one extra
What is the resistor colour code?
Black = Black
Beer = Brown
Rots = Red
Our = Orange
Young = Yellow
Guts = Green
But = Blue
Vodka = Violet
Goes = Grey
Well = Well
What is the tolerance of gold and silver on the resistor colour code?
Gold = 0.1 -/+ 5%
Silver = 0.01 +/- 10%
The DCWV if a capacitor in a half wave circuit is _____
Peak of the source voltage
When a rheostat is shorted, what is the voltage across Vce?
0.1V
What is the photodiode or LED current rating
10- 50 ma
What is the range of voltage for a forward biased LED photodiode
1.2 - 3.6 V
