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SEM 6_EE 210 > CH 5_BOOK_OPERATIONAL AMPLIFIERS > Flashcards

CH 5_BOOK_OPERATIONAL AMPLIFIERS Flashcards

1
Q

What is an op amp?

A

An electronic unit that behaves like a voltage-controlled voltage source. It may also be regarded as a voltage amplifier with very high gain.

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2
Q

Op amps can also be used in making a voltage or current-controlled __________ source.

A

Current.

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3
Q

What can op amps do?

A
  • Sum signals.
  • Amplify a signal.
  • Integrate a signal.
  • Differentiate a signal.
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4
Q

What method do we use as a tool in analyzing ideal op amp circuits?

A

Nodal Analysis

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5
Q

List the different types of ideal op amp circuits covered in Ch 5.

A
  • Inverter
  • Voltage follower
  • Summer
  • Difference amplifier
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6
Q

An operational amplifier is designed so that it performs some __________ operations when external components, such as resistors and capacitors, are connected to its __________.

A

Mathematical, Terminals

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7
Q

An op amp is a passive or active circuit element?

A

Active

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8
Q

VIEW ONLY: A typical op amp.

A
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9
Q

What are the 5 important terminals of an op amp?

A
  1. Inverting input
  2. Non-inverting input
  3. Output
  4. Positive power supply (V+)
  5. Negative power supply (V-)
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10
Q

As an active element, the op amp must be powered by a __________ supply.

A

Voltage

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11
Q

VIEW ONLY: KCL equation for power supply currents

A
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12
Q

The output section of an op amp consists of a voltage-controlled source in __________ with the output resistance R_o.

A

Series

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13
Q

The input resistance R_i is the Thevenin equivalent resistance seen at the __________ terminals, while the output resistance R_o is the Thevenin equivalent resistance seen at the __________.

A

Input, Output

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14
Q

The differential input voltage V_d is given by what formula?

A

Where V_1 is the voltage between the inverting terminal and ground. And V_2 is the voltage between the non-inverting terminal and ground.

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15
Q

The op amp senses the difference between the two inputs, multiplies it by the __________ A, and causes the resulting voltage to appear at the __________.

A

Gain, Output

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16
Q

What is the formula for the output voltage?

A
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17
Q

A is called the “open-loop voltage gain” because?

A

It is the gain of the op amp without any exernal feedback from the output to the input.

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18
Q

VIEW ONLY: Typical ranges for op amp parameters.

A
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19
Q

A negative feedback is achieved when?

A

The output is fed back to the inverting terminal of the op amp.

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20
Q

What is the closed-loop gain?

A

When there is a feedback path from output to input, the ratio of the output voltage to the input voltage is called the closed-loop gain.

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21
Q

Why are op amps used in circuits with feedback paths?

A

Because as a result of the negative feedback, it can be shown that the closed-loop gain is almost insensitive to the open-loop gain A of the op amp.

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22
Q

A practical limitation of the op amp is that the magnitude of its output voltage cannot exceed what?

A

The input voltage.
(The output voltage is dependent on and is limited by the power supply)

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23
Q

The op amp can operate in which 3 modes? (Depending on the initial input voltage V_d)

A
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24
Q

VIEW ONLY: Op amp output voltage V_o as a function of the differential input voltage V_d. (Considering Saturation if circuit is not linear)

A
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25
Q

For Ch. 5, we will assume that op amps operate in the linear mode. This means that the output voltage is restricted by?

A
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26
Q

An op amp is ideal if it has which 3 characteristics?

A
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27
Q

VIEW ONLY: Ideal op amp model.

A
28
Q

The 2 important properties of the ideal op amp are?
Which 2 extremely important equations can be derived from these 2 properties?

A

1) The currents into both input terminals are zero (because of infinite input resistance).
2) The voltage between the two input terminals is zero.

29
Q

The 2 characteristics of an ideal op amp note that for voltage calculations the input port behaves as a __________ circuit, while for current calculations the input port behaves as a __________ circuit.

A

Short, Open

30
Q

VIEW ONLY: The inverting amplifier.

A

The non-inverting input voltage is grounded, and the inverting input voltage V_i is connected to the input through R_1and the feedback resistor R_f is connected between the inverting input and output.

31
Q

What is the goal in analyzing in inverting op amp?

A

To obtain the relationship between the input voltage V_i and the output voltage V_o.

32
Q

Which equations can be derived from an inverting op amp? (View inverting op amp diagram)

A
33
Q

Which 2 types of gain are associated with inverting op amps?

A

1) Closed-loop gain A_v
2) Open-loop gain A

34
Q

What does an inverting amplifier do to the input signal?

A

An inverting amplifier reverses the polarity of the input signal while amplifying it.

35
Q

With an inverting op amp, the gain is equal to?

A

Which means the gain depends only on the external elements connected to the op amp.

36
Q

VIEW ONLY: The noninverting amplifier.

A
37
Q

Which equations can be derived from a noninverting op amp? (View noniverting op amp diagram)

A
38
Q

A noninverting amplifier is an op amp circuit designed to?

A

Provide a positive voltage gain.

39
Q

Under what conditions does a noninverting op amp circuit become a voltage follower?

A
40
Q

A voltage follower is useful for?

A

Such a circuit has a very high impedance and is therefore useful as an intermediate-stage (or buffer) amplifier to isolate one circuit from another, as seen on image. The voltage follower minimizes interaction between the two stages and eliminates interstage loading.

41
Q

VIEW ONLY: The voltage follower.

A
42
Q

What is a summing amplifier?

A

The summing amplifier is an op amp circuit that combines several inputs and produces an output that is the weighted sum of the inputs.

43
Q

The summing amplifier is a variation of the __________ amplifier.

A

Inverting (can handle many inputs at the same time)

44
Q

VIEW ONLY: The summing amplifier.

A
45
Q

Which equations can be derived from a summing op amp? (View summing amp diagram)

A
46
Q

Difference amplifiers are used when?

A

Difference amplifiers are used in various applications where there is a need to amplify the difference between two input signals.

47
Q

What is a difference amplifier?

A

A device that amplifies the difference between two inputs but rejects any signals common to the two inputs.

48
Q

Difference amplifiers are the first cousins of the ________ amplifier.

A

Instrumentation

49
Q

VIEW ONLY: The difference amplifier

A
50
Q

Which equations can be derived from a difference amplifier? (View difference amp diagram)

A
51
Q

It is often necessary in practical applications to connect op amp circuits in __________ to achieve a large overall gain.

A

Cascade

52
Q

What is a cascade connection?

A

A head-to-tail arrangement of two or more op amp circuits such that the output of one is the input of the next.

53
Q

When the op amp circuits are cascaded, each circuit in the string is called a?
The original input signal is?

A

Stage, increased by the gain of the individual stage

54
Q

Op amp circuits have the advantage that they can be cascaded without changing their?

A

Input-output relationships (due to the fact that each ideal op amp circuit has infinite input resistance and zero output resistance)

55
Q

Since the output of one stage is the input to the next stage, the overall gain of the cascade connection is?

A

The product of the gains of the individual op amp circuits.

56
Q

What caution must one take in designing cascaded op amp circuits?

A
57
Q

VIEW ONLY: A three-stage cascaded connection.

A
58
Q

The instrumentation amplifier is an extension of the __________ amplifier in that it amplifies the difference between its input signals.

A

Difference

59
Q

An instrumentation amplifier typically consists of _____ op amps and _____ resistors.

A

3 op amps, 7 resistors

60
Q

VIEW ONLY: (a) The instrumentation amplifier with an external resistance to adjust the gain, (b) schematic diagram.

A
61
Q

Which equations can be derived from the instrumentation amplifier? (View instrumentation amp diagram)

A
62
Q

VIEW ONLY: The instrumentation amplifier rejects common voltages but amplifies small signal voltages.

A

The instrumentation amplifier amplifies small differential signal voltages superimposed on larger common-mode voltages. Since the common-mode voltages are equal, they cancel each other out.

63
Q

The instrumentation amplifier has which 3 major characteristics?

A
64
Q

READ ONLY: The LH0036 instrumentation amplifier.

A
65
Q

VIEW ONLY: Summary of basic op amp circuits.

A
66
Q

READ ONLY: Op Amp Summary.

A

SEM 6_EE 210 (8 decks)

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