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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
How is a circuit stabilized in closed loop mode>
Negative Feedback is used but this also reduces circuit gain
25
Is the input resistance of the Op Amp high or low?
It is Very High
26
Is the input resistance of a non-inverting amp higher or lower that inverting?
Much Higher in a non-inverting
27
What Circuits are Summing Amplifiers used? (common uses)
Digital to analogue converters Analogue computers Audio Mixers
28
Is the integrator output voltage proportional or in-proportional to the input voltage
It is Proportional to the input voltage integrated over time
29
The Output of a Differentiator is proportional to the rate of change of what?
The input waveform
30
3 stages of coupling?
RC Transformer Direct
31
Most widely used type of coupling?
RC
32
Best Coupling for small signal amps?
RC
33
Best coupling for maximum voltage transfer?
Transformer
34
Best Coupling for a wideband of frequencies
Direct Coupling
35
Main Aim of a RC Coupled circuit?
To block DC and Couple the AC signal with minimum attenuation
36
Does a step up transformer increase or decrease the signal level?
Increases Signal level ( voltage gain )
37
At low frequency of a Coupled Transformer the gain is affected by?
The shorting affect of INDUCTIVE REACTANCE
38
Advantages of Transformer Coupling over RC?
Provides Impedance matching Voltage Gains are obtainable Lower power supply voltages are used Can be used for phase splitting
39
Disadvantages of Transformer Coupling?
Bulky and weight Cost Suffers from magnetic saturation Frequency range is limited
40
Advantages of Direct coupling?
Uniform gain over wide range of frequency Suited to low frequency application's
41
Disadvantages of Direct Coupling
No electrical isolation or power supply decoupling Not as stable, prone to drift
42
What is the purpose of a transformer core?
to provide a circuit of low resistance for the magnetic flux
43
Why can't transformers be operated at ranges below its normal operating range
Because Inductive Reactance (XL) will decrease, which will cause current to increase and if too high can damage the transformer
44
What is Ripple Frequency
The frequency of the AC component that is superimposed on the output
45
For a half-wave rectifier is ripple frequency the same or less than the input
Same
46
How is the average value of the voltage or current obtained in a full wave rectifier?
0.637 x peak voltage or current
47
Disadvantages of a full wave rectifier?
A centre-tapped transformer is required The Diode PIV is double that for a half wave rectifier
48
Disadvantages of a bridge rectifier
Greater forward voltage drop
49
In a full wave rectifier ( with a capacitor filter ) the amount of capacitor voltage fall is dependent on?
The Load current
50
Whats the result of adding a Inductor filter ?
The output ripple is decreased
51
RC Filter operation
These are added where ripple must be held to minimum
52
With push-pull operation best class of amplifier to use
Class B
53
Class C amplifier can be used in?
either single ended or push pull amplifiers
54
The bleeder resistor in a LC or Choke provides what?
A discharge path for the capacitor for when the supply is turned off
55
Ideally what should load regulation be?
Zero
56
Two Main methods of Voltage Reguation?
Series & Shunt
57
Advantages of a Capacitor Filter ?
Simple High Output voltage Good smoothing
58
Switch mode operation in a switch regulator produces?
A regulated DC output from a DC or AC Input
59
Advantages of Switch mode operation
Transformer & filter components smaller & lighter Better Efficiency
60
What is the overall gain in a Darlington transistor ?
B ^ 2 / Beta sqaured
61
What causes drift?
Temperature Power Supply Variations Ageing Components
62
What Cures Drift ?
Temp Compensation circuits Regulated power supplies
63
Power amplifiers give a large amount of what to the output?
Current
64
Do Audio Frequency Amplifiers have low or high output impedance?
Low output impedance
65
Do Audio Frequency Amplifiers have low or high input impedance?
High input impedance
66
Theoretical Efficiency of a Single Ended AF Power Amp
50%
67
Practical Efficiency of a Single Ended AF Power AMP
25-30%
68
How is crossover distortion reduced?
Via a resistive potential divider circuits or Diode Biasing
69
Phase splitting transformer must have ?
A Centre Tap
70
What are the requirements of the Barkhausen criteria?
The feedback factor must be exactly 1
71
Methods to control feedback factor?
Automatic Bias Amplitude Dependent Feedback Automatic Gain control
72
In a resonant LC oscillator if all current flows is it series or shunt fed?
Series if All Shunt if NONE
73
What is a colpitt oscillator characterized by?
split capacitance
74

PE4505 Flash Cards (6 decks)

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