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B1-4 > MOS > Flashcards

MOS Flashcards

1
Q

What carriers live in the p-type semiconductor which contains many holes??

A

Majority carriers and is of a net positive charge.

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2
Q

The n type semiconductor has?

A

Excess electrons (negative charge)

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3
Q

What happens at the point of contact when a p and n type material come together?

A

The holes in the P type material attract electron in the N type material. this point of contact is known as the PN junction

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4
Q

At the point of contact with a P and n material the p region contains?

A

A few thermally generated free electrons (minority carriers)

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5
Q

What forms the depletion region?

A

The formation of positive and negative charger on each side at the junction

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6
Q

The electric field in the depletion region acts as a barrier for the free electrons in the n region, how are they moved across the barrier?

A

An external energy must be applied to get the electrons to move across the barrier, .7V for silicon

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7
Q

What happens to the barrier potential with an increase in temperature?

A

Conductance is increased, causing the barrier potential (voltage required to decrease)

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8
Q

Why are resistors used in a diode circuit?

A

Limits the current to a value that will not damage the PN structure of the diode.

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9
Q

In forward bias when does a diode turn on in relation to the graphing curve?

A

At the knee (0.7V) where the voltage practically stops but the current sky rockets.

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10
Q

Explain resistance within a diode.

A

Diode resistance in forward bias is very minimal, in reverse bias it is very high.

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11
Q

Explain dynamic resistance of a diode.

A

The resistance is greatest below the knee of the curve because the current increases very little until it reaches 0.7. as it reaches 0.7 the sharp increase of current causes the resistance to reduce practically to none.

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12
Q

What happens to the depletion regions when a diode is placed in reverse bias and voltage applied?

A

With voltage applied the electric field is higher which widens the depletion region which in turn DECREASES the probability that current carriers can make the jump across it.

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13
Q

Describe the relationship between voltage and current in reverse BIAS

A

With Voltage applied there is a very very small amount of current passing (leakage current) With 0 Volts applied there is absolutely no current. As voltage is gradually increased there is a constant very small current passing, until voltage hits breakdown which causes failure and the current spikes. (Downwards on the graph)

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14
Q

Why are diodes used in series?

A

They are used to increase the reverse blocking capabilities in many high voltage applications

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15
Q

What is a problem with diodes in series?

A

The reverse current leakage ratings are always different during process, the diode with the highest resistance will also have a higher voltage across it causing it to fail which in turn fails the other diode.

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16
Q

How is the problem over series diodes overcome?

A

By adding in a high value resistor in parallel with each diode., (parallel sharing resistors) This will bring the reverse voltage that is applied across the diodes =

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17
Q

Why are diodes used in parallel?

A

Increases forward current rating. (diodes with equal current sharing should be achieved other wise the use of resistors will be needed)

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18
Q

What is a problem in relation to diodes in parallel?

A

If the diodes have varying current capacities, the diode with the lowest forward voltage drop will try to carry a large current, which may damage it.

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19
Q

When connecting diodes in parallel, if the diodes exact characteristics are not known what should be done?

A

Sharing resistors can be used ( Resistors in series with diodes but parallel to each other)

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20
Q

What is a rectifier diode and what is it used for?

A

Rectifier diodes are simply diodes redesigned to serve the purpose of rectifying AC current, The circuit symbol for diodes and rectifier diodes are the same.

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21
Q

What are the primary uses of a rectifier diode?

A

Half wave and full wave rectifiers, and a DC Blocker. They are also used to convert AC to DC voltage.

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22
Q

How does a half wave rectifier work?

A

By converting the positive portion of a sine wave to DC through 1 diode, when the AC sine wave turns to the negative direction this reverse biases the diode blocking the AC.

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23
Q

How does a full wave rectifier work?

A

By using 2 or more diodes arranged so that load/output current flows in the same direction during each half cycle of the AC input signal.

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24
Q

How does a bridge rectifier work?

A

By using a 4 diodes arranged in a diamond shape allowing current to flow through the load during both half cycles of the applied voltage, this bridge rectifier is a full wave rectifier.

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25
Q

What is an advantage of the bridge rectifier?

A

Produces a voltage output that is nearly twice that of the conventional full wave circuit

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26
Q

Where are SCR thyristors mainly used?

A

Motor speed controls, light dimmers, pressure control systems.

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27
Q

How an a diode be forced into breakdown?

A

By applyging a reverse bias across the diode.

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28
Q

Describe a nonlinear circuit

A

It is a discrete (digital) circuit, meaning it doesnt deal with analogue type data. 1 & 0’s

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29
Q

Describe a logic circuit.

A

Perform logic on a given discrete input using logic gates (AND, OR, NOT)

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30
Q

What is a logic integrated circuit?

A

A singular electronic device which contains entire logic circuits within. Large IC’s can house thousands to billions of transistors within and can perform very complex logic.

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31
Q

Describe a Linear Circuit and their uses.

A

An analogue type of circuit which contains an entire linear circuit within , OP Amps, Voltage regulators, communication circuits, interface circuits.

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32
Q

The ideal OP AMP has what characteristics?

A
  1. Infinite Voltage gain (20,000 to 200,000)
    2.An infinite input impedance. (2Mohm)
    3.A zero output impedance (75 ohm)
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33
Q

What do they mean when they say an OP AMP is operating in OPEN-LOOP?

A

Driven until as close to the supply voltage as it could get (saturation)

34
Q

In an OP AMP if the output is to be larger than the input how is the massive amplification of the output controlled?

A

By using a feedback loop. part of the output voltage is fed back to the input and referred to as feedback.

35
Q

How does a Op-Amp Voltage Follower make sure the output is the same as the input?

A

The feedback resistor is the same value as the input resistor.

36
Q

What are the 2 purposes of the OP AMP Voltage follower?

A

To have the same output as the input. or to have the same input and output values but the signal (sinewave) reversed.

37
Q

What is the term used for seperately packaged components?

A

Discrete components

38
Q

Miniaturised electronic equipment is called?

A

microelectronics

39
Q

Complex devices that contain complete circuits packaged as a single component are referred to as?

A

Integrated circuits.

40
Q

What is a intergrated circuit?

A

A device which incorportates both active components (transistors, diodes) and passive components resistors, capacitors) into a tiny chip.

41
Q

What are some advantages of a integrated circuit?

A

Drastic reduction in size and weight.
Large increase in reliability
Lower costs
Lower power consumption
Less heating load

42
Q

What is the only disadvantage to a integrated circuit?

A

Repair becomes impossible, the entire circuit is replaced as a single component.

43
Q

What is a PCB?

A

Flat insulating surface upon which printed wiring (copper, silver, gold) and components are connected.

44
Q

What is the purpose of the PCB?

A

To provide electrical connections between the components mounted to it.

45
Q

What are PCB’s made from?

A

flat laminated composite made from non conductive materials.

46
Q

What is the base/substrate made of for a PCB?

A

Phenolic paper, epoxy paper and epoxy glass.

47
Q

How are the wires formed on the surface of the copper?

A

The copper foil is etched away leaving behind the wire patterns referred to as CONDUCTOR PATTERNS, or TRACKS.

48
Q

What gives the PCB’s their green colour?

A

Solder mask, this is an insulating protective coat that protects the thin copper wires from corrosion.
Silk Screen is then printed on top which is the text or images of components.

49
Q

What is through hole technology?

A

The components are pushed through from the insulating side (component side) and the wires them selves are solderd on the copper side (Solder side)

50
Q

Explain surface mounted technology

A

SMT are mounted on the same side as the conductor pattern, therefore it does not require a hole in the board. these are much smaller , they are now also cheaper then THT

51
Q

What are Voltage and ground lines or planes on a PCB?

A

long and slender pathways that provide power to components on board.

52
Q

If a component needs to be removed from a PCB what is installed?

A

Sockets

53
Q

What is the purpose of an edge connector on a PCB?

A

Connecting one PCB to another PCB

54
Q

What are single sides PCBs?

A

Components on one side and conductor pattern on the opposite, sever limitations when it comes to routing wires.

55
Q

describe double sided PCB’s

A

Conductor patterns on both side of the board. they use VIAS to connect one side of the PCB to the other. much more suited for complex circuits better for wire routing.

56
Q

Describe multi layer PCB’s

A

Sandwich of later, alternating between nonconducting dielectric layer and the copper foil.

57
Q

What is the purpose of the PCB substrate?

A

Not conduct electricity Porcelain,mica,glass,plastics, quality is important to avoid delamination and must be heat resistant.

58
Q

What is the most common dielectric?

A

FR-4 Epoxy glass cloth, FR stands for flame retardant and CEM means composite epoxy materials.

59
Q

What is the reasoning behind copper foil weights.

A

Higher weights allow more current to be carried for a particular track width.

60
Q

What are the pads used for on a PCB?

A

Provide the copper surface that legs of a component will be soldered to. Pad size should be 1:8 times the diameter of the hole. Pad to hole ratio is important.

61
Q

What is the purpose of the VIAS on a PCB?

A

Its merely used to connect one side of the PCB to the other side of a PCB if there were to conducting patterns on each side.

62
Q

What kind of Vias are there?

A

Through vias - Right through board, blind vias - outside board to inside board. and buried vias - internal connections

63
Q

There is no ruling for tracks on a PCB but what is the general rule of thumb?

A

The bigger the track the better, lower dc resistance, lower inductance, easier to inspect. Track width will be dictated by current flowing through it.

64
Q

With clearances on a PCB what is creepage?

A

Shortest ditance between conductor traces on a PCB

65
Q

What are the advantages of a multilayer board?

A

lot of extra density to route power and signal tracks by having the signals run on the inside of the board (Ground planes and power planes)

66
Q

Advantages of power planes?

A

Reduce power wiring inductance and impedance to components, vital for highspeed digital design.

67
Q

What are the 2 main classes of servomrchanism?

A

position control and speed control

68
Q

In a Servomechanism what does the controller do?

A

Manages or controls the entire system, computer processir

69
Q

In a Servomechanism what does the Disturbance do?

A

Something that forces the output of a system to change without a demanded change at the input. EG: turbulent winds

70
Q

In a Servomechanism what does the Feedback do?

A

Feedback can be mechanical shaft or gear, physical movement or an electrical signal which provides an actual response to a desired response. Modern aircraft used a transducer to convert mechanical to electrical feedback.

71
Q

In a Servomechanism what does the Null point.

A

The field quantity is at ZERO, two ore more opposing forces at the null point cancel each other out.

72
Q

In a Servomechanism what does the Summing point?

A

Error signals are modified by other factors such as output rate or position.

73
Q

In a Servomechanism what does the Transducer do?

A

Convert one form of energy into another.. EG temp changes into electrical voltages etc.

74
Q

Describe open loop control.

A

Control action is independent of the output, does not self correct when disturbances causes out drift resulting in large deviations. Sometimes uses timers to help correct errors.

75
Q

Describe control systems and feedback

A

General term for any system that manages commands, directs or regulates the behaviour of the other devices or systems using control loops.

76
Q

Describe a closed loop system.

A

Feed back is added to the system, measures the difference between actual output and the demanded result by using the difference, much more accurate.

77
Q

What is the purpose of the follow up system?

A

An error feedback signal that is used to return the aircraft to stable flight at the selected altitude or heading. As the aircraft is approaching the heading or altitude the follow up signal is sent to correct the aircraft.q

78
Q

What does the analogue transduce do?

A

Converts mechanical to electrical output in the feedback system to be processed by the controller.

79
Q

Passive transducer require external excitation. Active transducer dont require a external excitation what are some examples

A

Thermocouple, tachogenerator.

80
Q

How does the hall effect transducer work?

A

Phenomenon that the EMF forces appears in the direction perpendicular to both the current and the magnetic field. Flux direction is pushed to one side and its density and direction are measured.

81
Q

What are the 2 digital transducers and decribe their operation.

A

Incremental encoder (LED wheel) - Uses square wave outputs which then converts into a numerical position
Absolute Encoder (Hypnotising wheel) - Many light sources and inputs but the output is an accurate binary number.

B1-4 (4 decks)

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