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Multiple choice properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

An infinite impedance for an ideal opamp implies

  1. Opamp doesn't draw any current through its terminals

  2. Opamp draws only 10 micro amperes for its function

  3. Opamp's inverting terminal draws no current

  4. Opamp's non inverting terminal draws no current
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Since input impedance for an ideal opamp is infinite, the current drawn will be zero 

Multiple choice properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

A voltage follower 

  1. has a voltage gain of 1

  2. is noninverting

  3. has no feedback resistor

  4. has all of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

a voltage follower is a circuit, wherein the magnitude and the phase of the signal remains the same. In order to achieve it, the feedback signal should be fed to positive terminal, so that phase is unchanged and the absence of a feedback resistor makes no loss in the output signal

Multiple choice properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

As the supply voltage increases, the voltage gain of the circuit _____ and the power consumption _____.

  1. increases, increases

  2. increases, decreases

  3. decreases, decreases

  4. decreases, increases
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Increasing the supply voltage to an op-amp generally allows for a larger output swing (increasing gain potential) and increases the quiescent power consumption of the device.

Multiple choice properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

Open loop gain of an amplifier can be represented by the formula

  1. $\dfrac{V _0}{V _i}$

  2. $V _0+V _i$

  3. $V _0-V _i$

  4. $V _0 \times V _i$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Open loop gain of an amplifier is the ratio of output voltage to the input voltage difference that is being amplified.

$\therefore$ open loop gain $A _{OL}$$=\cfrac{V _{out}}{V^+-V^-}\simeq\cfrac{V _{out}}{V _i}$
Since it is the gain obtained when no overall feedback is used in the circuit.

Multiple choice properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

Which of the following AC parameters of an Op-amp results in reduction of output voltage if it becomes excessive?

  1. Transient Response

  2. Slew Rate

  3. Bandwidth

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The significant AC parameters of Op-amp are transient response, bandwidth and slew rate but all of them have different results while becoming excessive. The transient response affects the settling time while slew rate give rise to distortion if exceeded. As a result, bandwidth reduces the output voltage when it is exceeded. 

Since bandwidth is a small signal phenomenon, it represents the band of frequencies for which the gain remains constant & also highly dependable on compensating components including closed loop gain. But, it exhibits adverse consequences in the reduction of an output voltage when exceeded to greater extent.

Multiple choice properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

In a differential connection, the signals that are opposite at the inputs are _____ amplified, and those that are common to the two inputs are _____ amplified.

  1. slightly, slightly

  2. slightly, highly

  3. highly, highly

  4. highly, slightly
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Differential amplifiers are designed to amplify the difference between two signals (highly amplified) while rejecting signals common to both inputs, such as noise (common-mode rejection, slightly amplified).

Multiple choice properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

Current cannot flow to ground through

  1. A mechanical ground

  2. An ac ground

  3. A virtual ground

  4. An ordinary ground
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  1. Virtual ground refers to a circuit elements that is not connected to the ground directly, it is held at a reference voltage. This reference voltage need not to be same voltage as ground either.
    2. While in all other ground it may be mechanical A.C or an ordinary ground it act as a reference point against which other voltage can be measured.
    3. The key point  is that the current flow from one point of the circuit through ground then back into the circuit.
    So, current cannot flow to ground through a virtual ground.
Multiple choice properties of an ideal op-amp electronics physics the operational amplifier (op-amp)

Why are the Op-amps with open loop configuration not used in linear applications?

  1. High risk of distortion

  2. High risk of clipping of output signal

  3. Both a & b

  4. works as an attenuator
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Open loop configuration of Op-amp may increase the threat of distortion as well as clipping of output signal. Due to this reason, the output gets switched between the positive and negative saturation levels.

Hence, this is the major drawback because of which it is highly impossible to use Op-amps with open loop configurations in linear circuit applications.