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PE4505 Flash Cards > Exam 2 - 3.1 to 3.5.15 > Flashcards

Exam 2 - 3.1 to 3.5.15 Flashcards

Use if u wanna die

1
Q

What is an “Op Amp”?

A

A very high gain (Voltage) , direct coupled amplifier with provision for feedback that can be used to control its response

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1
Q

Three stages of a Op Amp

A
  • A differential amp (INPUT)
  • Several high gain voltage amp stages ( SECOUND )
  • An output ( power ) amplifier ( FINAL )
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2
Q

The Op Amp input stage gives what characteristics?

A

High Common mode rejection
Differential Inputs
A Frequency response down to DC ( DC-Amp )
Very high input impedance
Less Drift

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3
Q

What class is the final stage in a Op Amp

A

Class B

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4
Q

What should the ideal voltage gain ( open loop ) be in a op amp?

A

Infinite

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5
Q

What should the ideal Bandwidth be in a op amp?

A

Infinite

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6
Q

What should the ideal Input impedance be in a op amp?

A

Infinite

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7
Q

What should the ideal Output Impedance be in a op amp?

A

Zero

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8
Q

What is Offset in a Op Amp?

A

If the differential input voltage is zero, a small DC output voltage will result

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9
Q

How is the offset in a Op Amp cancelled or compensated?

A

Via External circuitry .

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10
Q

How is a Op Amp powered?

A

By both negative and positive power supplies (split supplies)

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11
Q

How can a differential pair amp be used with a single-ended input?

A

If one of the inputs is grounded or fixed to a reference voltage

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12
Q

What kind of circuit’s are Differential Amps found

A

Circuits that utilize series negative feedback

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13
Q

Common Applications for Differential Amplifiers

A

Control of motors & servos
Signal Amplification

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14
Q

What is Rejection effective at removing?

A

Large Part of noise
DC bias common to both inputs

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15
Q

What is input offset voltage?

A

Applies a small DC differential voltage to force the output DC to zero

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16
Q

What is the slew rate?

A

An indication of how fast the output voltage of the Op Amp can change

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17
Q

What can the bandwidth of an Op Amp be specified as?

A

The First Breakout point
Frequency at which the gain falls to unity
The full power bandwidth
The Gain bandwidth product

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18
Q

Is Positive feedback regenerate or degenerative ?

A

Regenerative

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19
Q

Is negative feedback regenerate or degenerative ?

A

Degenerative

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20
Q

Is Gain decreased or increased with NEGATIVE feedback?

A

Decreased

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21
Q

Is Gain Stability increased or decreased with POSITIVE feedback?

A

Decreased

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22
Q

Is Amp Distortion increased or decreased with POSITIVE feedback?

A

Increased

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23
Q

Is Amp Noise increased or decreased with POSITIVE feedback?

A

Increased

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24
Q

How is a circuit stabilized in closed loop mode>

A

Negative Feedback is used but this also reduces circuit gain

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25
Q

Is the input resistance of the Op Amp high or low?

A

It is Very High

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26
Q

Is the input resistance of a non-inverting amp higher or lower that inverting?

A

Much Higher in a non-inverting

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27
Q

What Circuits are Summing Amplifiers used? (common uses)

A

Digital to analogue converters
Analogue computers
Audio Mixers

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28
Q

Is the integrator output voltage proportional or in-proportional to the input voltage

A

It is Proportional to the input voltage integrated over time

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29
Q

The Output of a Differentiator is proportional to the rate of change of what?

A

The input waveform

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30
Q

3 stages of coupling?

A

RC
Transformer
Direct

31
Q

Most widely used type of coupling?

A

RC

32
Q

Best Coupling for small signal amps?

A

RC

33
Q

Best coupling for maximum voltage transfer?

A

Transformer

34
Q

Best Coupling for a wideband of frequencies

A

Direct Coupling

35
Q

Main Aim of a RC Coupled circuit?

A

To block DC and Couple the AC signal with minimum attenuation

36
Q

Does a step up transformer increase or decrease the signal level?

A

Increases Signal level ( voltage gain )

37
Q

At low frequency of a Coupled Transformer the gain is affected by?

A

The shorting affect of INDUCTIVE REACTANCE

38
Q

Advantages of Transformer Coupling over RC?

A

Provides Impedance matching
Voltage Gains are obtainable
Lower power supply voltages are used
Can be used for phase splitting

39
Q

Disadvantages of Transformer Coupling?

A

Bulky and weight
Cost
Suffers from magnetic saturation
Frequency range is limited

40
Q

Advantages of Direct coupling?

A

Uniform gain over wide range of frequency
Suited to low frequency application’s

41
Q

Disadvantages of Direct Coupling

A

No electrical isolation or power supply decoupling
Not as stable, prone to drift

42
Q

What is the purpose of a transformer core?

A

to provide a circuit of low resistance for the magnetic flux

43
Q

Why can’t transformers be operated at ranges below its normal operating range

A

Because Inductive Reactance (XL) will decrease, which will cause current to increase and if too high can damage the transformer

44
Q

What is Ripple Frequency

A

The frequency of the AC component that is superimposed on the output

45
Q

For a half-wave rectifier is ripple frequency the same or less than the input

A

Same

46
Q

How is the average value of the voltage or current obtained in a full wave rectifier?

A

0.637 x peak voltage or current

47
Q

Disadvantages of a full wave rectifier?

A

A centre-tapped transformer is required
The Diode PIV is double that for a half wave rectifier

48
Q

Disadvantages of a bridge rectifier

A

Greater forward voltage drop

49
Q

In a full wave rectifier ( with a capacitor filter ) the amount of capacitor voltage fall is dependent on?

A

The Load current

50
Q

Whats the result of adding a Inductor filter ?

A

The output ripple is decreased

51
Q

RC Filter operation

A

These are added where ripple must be held to minimum

52
Q

With push-pull operation best class of amplifier to use

A

Class B

53
Q

Class C amplifier can be used in?

A

either single ended or push pull amplifiers

54
Q

The bleeder resistor in a LC or Choke provides what?

A

A discharge path for the capacitor for when the supply is turned off

55
Q

Ideally what should load regulation be?

A

Zero

56
Q

Two Main methods of Voltage Reguation?

A

Series & Shunt

57
Q

Advantages of a Capacitor Filter ?

A

Simple
High Output voltage
Good smoothing

58
Q

Switch mode operation in a switch regulator produces?

A

A regulated DC output from a DC or AC Input

59
Q

Advantages of Switch mode operation

A

Transformer & filter components smaller & lighter
Better Efficiency

60
Q

What is the overall gain in a Darlington transistor ?

A

B ^ 2 / Beta sqaured

61
Q

What causes drift?

A

Temperature
Power Supply Variations
Ageing Components

62
Q

What Cures Drift ?

A

Temp Compensation circuits
Regulated power supplies

63
Q

Power amplifiers give a large amount of what to the output?

A

Current

64
Q

Do Audio Frequency Amplifiers have low or high output impedance?

A

Low output impedance

65
Q

Do Audio Frequency Amplifiers have low or high input impedance?

A

High input impedance

66
Q

Theoretical Efficiency of a Single Ended AF Power Amp

A

50%

67
Q

Practical Efficiency of a Single Ended AF Power AMP

A

25-30%

68
Q

How is crossover distortion reduced?

A

Via a resistive potential divider circuits or
Diode Biasing

69
Q

Phase splitting transformer must have ?

A

A Centre Tap

70
Q

What are the requirements of the Barkhausen criteria?

A

The feedback factor must be exactly 1

71
Q

Methods to control feedback factor?

A

Automatic Bias
Amplitude Dependent Feedback
Automatic Gain control

72
Q

In a resonant LC oscillator if all current flows is it series or shunt fed?

A

Series if All
Shunt if NONE

73
Q

What is a colpitt oscillator characterized by?

A

split capacitance

74
Q
A

PE4505 Flash Cards (6 decks)

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