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 \(V_{o}=\left(1+\dfrac{R_{F}}{R_{A}R_{B}R_{C}}\right)\left[\dfrac{V_{A}}{R_{A}}+\dfrac{V_{B}}{R_{B}}+\dfrac{V_{C}}{R_{C}}\right]\) Choose the most appropriate answer from the options given below :
(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 frequencies
(B) and (E) Only
Only (B) and (E) survive — option 4 — and the other three each invert or garble a standard result.
(A) is wrong on two counts. The inverting summer's output is
\(V_{o}=-R_{F}\left(\dfrac{V_{A}}{R_{A}}+\dfrac{V_{B}}{R_{B}}+\dfrac{V_{C}}{R_{C}}\right)\)
First, an inverting configuration must produce a minus sign, and the statement has none. Second, its factor \(\left(1+R_{F}/R_{A}R_{B}R_{C}\right)\) is dimensionally impossible — adding 1 to a resistance divided by the product of three resistances gives units of reciprocal ohms squared. The correct expression simply multiplies the sum of input currents by \(R_{F}\), since all three currents meet at the virtual earth.
(B) is correct. The difference amplifier with matched resistors gives
\(V_{o}=\dfrac{R_{F}}{R_{1}}\left(V_{+}-V_{-}\right)\)
and with unity gain that is exactly the non-inverting input minus the inverting input, as stated.
(C) confuses two opposite filters. A notch filter is a narrow band-reject filter: it removes a narrow band and passes everything else, which is how mains hum at 50 Hz is eliminated. A narrow band-pass filter does the reverse. The two have complementary responses, so calling one by the other's name is a clear error.
(D) is backwards. VCO stands for voltage-controlled oscillator — a voltage in, a frequency out, so it is a voltage-to-frequency converter. The frequency-to-voltage converter is the opposite device, as Q13 of this paper describes.
(E) is correct, and describes exactly what an all-pass filter is for. Its magnitude response is flat at unity for every frequency:
\(H(s)=\dfrac{s-a}{s+a},\qquad \left|H(j\omega)\right|=1\)
while its phase varies from 0° to −180°. Since it changes nothing about amplitude, its whole purpose is phase — delay equalisation in transmission lines, phase shifters in SSB modulators, and correcting the group delay of other filters.
Hence, the correct statements are (B) and (E).
Similar Questions
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.
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.
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 :
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:
The correct flow in the basic block diagram of op-Amp is
A. Complementary symmetry push pull amplifier block.
B. Dual input unbalanced output differential amplifier block
C. Emitter follower with constant current source block
D. Dual-Input balanced output differential amplifier block
Choose the correct answer from the options given below :
Match the following :
List - I List - II a) 
i) 
b) 
ii) 
c) 
iii) 
d) 
iv) 
Codes :
Important Questions from Op-Amp and Its Applications
In the circuit shown below, $R$ is $1\text{ k}\Omega$ and $R_f$ is $10\text{ k}\Omega$. If $V_{\text{in}}$ is $100\text{ mV}$ and the op-amps have supply voltages of $\pm 15\text{ V}$, then $V_{\text{out}}$ is _______ V.
For IC 741 circuit shown below, the maximum input frequency above which the output will be distorted is ____________.
Assume that an op-amp 741 connected as a unit gain inverting amplifier is applied with an input change of 10 V. Determine the time taken for the output to change by 10 V. [Slew rate for op-amp 741 = 0.5 V/µs]
What is the value of output voltage $V_o$ in the given circuit? Assume op-amp to be ideal and MOSFET operating in saturation region.
In an ideal op-amp, the common mode gain is _____________.
