Tag: physics

Questions Related to physics

An infinite impedance for an ideal opamp implies

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

  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

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Correct Option: A
Explanation:

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

A voltage follower 

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

  1. has a voltage gain of 1

  2. is noninverting

  3. has no feedback resistor

  4. has all of these

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Correct Option: D
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

The voltage between the input terminals of an ideal op amp is

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

  1. Zero

  2. Very small

  3. Very large

  4. Equal to the input voltage

Show answer
Correct Option: A
Explanation:

The input impedance of an ideal opamp is infinite and hence the current through it is zero. Thus the voltage across the terminals is also zero

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

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

  1. increases, increases

  2. increases, decreases

  3. decreases, decreases

  4. decreases, increases

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Correct Option: A

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

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

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

  2. $V _0+V _i$

  3. $V _0-V _i$

  4. $V _0 \times V _i$

Show answer
Correct Option: A
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.

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

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

  1. Transient Response

  2. Slew Rate

  3. Bandwidth

  4. All of the above

Show answer
Correct Option: D
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.

 Of the values listed, the most realistic value for open-loop voltage gain of an OP-amp is

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

  1. 1

  2. 2000

  3. 80 dB

  4. 100000

Show answer
Correct Option: D
Explanation:

Open loop voltage in an opamp is very high and hence option d is the correct option

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.

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

  1. slightly, slightly

  2. slightly, highly

  3. highly, highly

  4. highly, slightly

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Correct Option: D

Current cannot flow to ground through

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

  1. A mechanical ground

  2. An ac ground

  3. A virtual ground

  4. An ordinary ground

Show answer
Correct Option: C
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.

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

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

  1. High risk of distortion

  2. High risk of clipping of output signal

  3. Both a & b

  4. works as an attenuator

Show answer
Correct Option: C
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.