Tag: the operational amplifier (op-amp)

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

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

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In an ideal op-amp circuit, the gain is independent of the frequency of the input signal within the bandwidth. If the 1000 Hz signal is amplified by 20 times, other signals within the bandwidth will also be amplified by the same factor.

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

The ideal opamp has the following characteristics

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

The open loop voltage gain in an opamp 

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
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

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.