Tag: electronics

Questions Related to electronics

An AC signal with frequencies 1000 Hz, 1500 Hz and 2500 Hz are fed to the inverting terminal of an opamp. The voltage level of all these signals are 2V. If 1000 Hz signal is amplified by 20 times, then

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

  1. 2500 Hz signal will get amplified by 50 times

  2. 2500 Hz signal will get amplified by 20 times

  3. 1500 Hz signal will get amplified by 15 times

  4. 2500 Hz signal will get amplified by 10 times

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Correct Option: B

The ideal opamp has the following characteristics

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

  1. Input resistance = Infinity; Voltage gain = Infinity

  2. Input resistance = zero; Voltage gain = Infinity

  3. Input resistance = zero; Voltage gain = zero

  4. Input resistance = Infinity; Voltage gain = zero

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Correct Option: A
Explanation:

The ideal op-amp has infinite high input resistance and infinite voltage gain.

The ideal op-amp will have infinite voltage gain.Op-amp are devices that many times are used to function as amplifiers. A voltage is input into the op-amp and as output, it produces the voltage amplified.
An ideal op-amp will have infinite high input resistance.This will ensure that the op-amp causes no loading in the circuit.

The open loop voltage gain in an opamp 

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

  1. reduces if voltage across the inverting and non inverting terminal are same

  2. reduces if voltage across the inverting terminal is zero

  3. increases if voltage across the inverting and non inverting terminal are same

  4. remains the same, if voltage across any of these terminals are changed

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Correct Option: C
Explanation:

Open loop voltage gain is given by $A _v=\dfrac{V _0}{V _+-V _-}$. If $V _+=V _-$, Voltage gain becomes infinity or very high. thus voltage gain increases

Which of the following electrical characteristics is not exhibited by an ideal op-amp?

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

  1. Infinite voltage gain

  2. Infinite bandwidth

  3. Infinite output resistance

  4. Infinite slew rate

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Correct Option: C
Explanation:

An ideal op-amp exhibits zero output resistance so that output can drive an infinite number of other devices.

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

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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. $V _0 \times V _i$

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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

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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.