Assertion (A) : An Op-Amp is a direct coupled high gain amplifier. Reason (R) : It consists of one or more differential amplifiers and usually followed by a level translator and push pull stage.
Both (A) and (R) are correct and (R) is correct explanation of (A).
Both statements are true, and the reason gives the internal structure that produces exactly the properties the assertion names — option 1.
The assertion. An operational amplifier is direct coupled — no capacitors between stages — and has a very large open-loop gain, typically \(10^{5}\) to \(10^{6}\), or 100 to 120 dB. Both facts are standard.
The reason explains both. Take the three stages named in turn:
| Stage | Contribution |
|---|---|
| Differential amplifier input | High gain; high common-mode rejection; directly coupled by nature |
| Level translator | Restores the DC level that direct coupling has shifted |
| Push-pull output | Low output impedance, current drive in both directions |
Why the coupling must be direct. An op-amp is required to amplify down to DC — it must respond to a steady difference between its inputs, since that is what integrators, comparators and precision references depend on. A coupling capacitor blocks DC and would destroy this. Direct coupling is therefore not a design convenience but a requirement.
What direct coupling costs, and why the level translator exists. Each stage's output sits at some DC level well above ground, and connecting it straight to the next stage carries that offset forward, accumulating stage by stage until the output is driven towards a rail with no signal applied. The level translator — an emitter follower with a resistor or a constant-current source, or a diode-connected chain — shifts the level back down so that the output rests near zero for zero input. Direct coupling also lets drift and low-frequency noise through, which is why input offset voltage and its temperature drift are prominent specifications.
The differential input does the other essential job : it responds to the difference between the inputs and rejects what is common to both, so hum and supply variation appearing equally on both pins are suppressed — typically by 90 dB or more.
The answer is flagged only because the linkage is a matter of judgement: R describes the construction rather than deducing the properties. But the connection is direct and complete — the differential stages give the gain, and their direct coupling gives the DC response — so R does explain A.
Hence, both (A) and (R) are correct and (R) explains (A).
Similar Questions
The input to a differentiator is –5 V. Its output will be
Match the following :
List – I List – II a. h-parameters i. O/P voltage varies as the slope of i/p voltage b. differentiator ii. Noise division c. half-wave rectifier iii. Function of a Q point d. integrator iv. series diode clipper Codes :
Assertion (A) : Op-Amp is used for sensor circuit.
Reason (R) : A small signal amplifier amplify weak measured signals.
For an inverting comparator circuit acting as a Schmitt Trigger, as shown in figure below, the expression of Hysteresis Voltage (Vny) is given by :
Consider the following statements :
(A) The output voltage of a summing amplifier (inverting configuration) with three inputs VA, VB and VC and input resistors RA, RB and RC is \(V_{o}=\left(1+\dfrac{R_{F}}{R_{A}R_{B}R_{C}}\right)\left[\dfrac{V_{A}}{R_{A}}+\dfrac{V_{B}}{R_{B}}+\dfrac{V_{C}}{R_{C}}\right]\)
(B) In a subtractor circuit, the output voltage is equal to voltage applied to non-inverting terminal minus voltage applied to inverting terminal
(C) The narrow band pass filter is called a Notch filter
(D) VCO is also called as frequency to voltage
(E) The all pass filter provides unity-gain with predictable phase shifts for different input frequenciesChoose the most appropriate answer from the options given below :
Consider the following circuit, the switch S1 allows the output to switch between two ranges of amplitudes from 0-0.1 V and 0-1 V. Arrange these values of R1, R2 and R3 in increasing order.
(A) Value of R1
(B) Value of R2
(C) Value of R3Choose the most appropriate answer from the options given below :
Match List I with List II
LIST I LIST II A. Butterworth filter of order '2' I. Impedance matching B. Buffer II. CMRR = ∞ (infinity) C. Schmitt Trigger III. Positive feedback D. Ideal OPAMP IV. 40 dB/decade roll off Choose the correct answer from the options given below:
The given operational amplifier circuit corresponds to which electronic circuit application ?
Statements in connection to Op-Amp applications are :
A. If we use a square wave generator followed by integrator circuit we get a triangular wave at the output
B. The logarithmic amplifier called a log-amplifier or a logger, is basically a current to voltage converter.
C.
is a first order high pass filter with voltage followerD. If we use a square wave generator followed by a clipping circuit then we get a saw-tooth wave generator.
Choose the correct answer from the options given below:
Match List I with List II
LIST I LIST II A. Single polarity positive voltage clipper circuit I. 
B. Negative clamping circuit II. 
C. Differentiator circuit III. 
D. Logarithmic Amplifier IV. 
Choose the correct answer from the options given below:
Important Questions from Op-Amp and Its Applications
What is the typical value of open-loop voltage gain, AVOL, for a 741 op-amp?
An ideal Op-Amp is an ideal
- In an ideal OP-AMP, which one is correct?
Which of the following statements about the Op-Amp differential amplifiers is INCORRECT?
The total output offset voltage of an operational amplifier is a function of these effects.
