250+ TOP MCQs on Summing, Scaling & Averaging Amplifier – 2 & Answers

Linear Integrated Circuit Problemson “Summing, Scaling & Averaging Amplifier – 2”.

1. Which type of amplifier has output voltage equal to the average of all input voltages?
A. Inverting averaging amplifier
B. Non-inverting averaging amplifier
C. Non-inverting summing amplifier
D. Inverting scaling amplifier
Answer: B
Clarification: In non-inverting averaging amplifier, the non-inverting input voltage is the average of all inputs, with a positive sign.

2. Expression for output voltage of non-inverting summing amplifier with five input voltage?
A. V_o = 5×( V_a + V_b+ V_c+ V_d+ V_e)
B. V_o = [1+( R_f/R₁)]× ( V_a + V_b+ V_c+ V_d+ V_e)
C. V_o = V_a + V_b+ V_c+ V_d+ V_e
D. V_o = ( V_a + V_b+ V_c+ V_d+ V_e) /5
Answer: C
Clarification: The output voltage of non-inverting summing amplifier is (1+ ( R_f / R₁ )) times the average of all input voltages in the circuit.
Since there are five input voltages => (1+ ( R_f / R₁ )) =5
Therefore, V_o = 5×( V_a + V_b+ V_c+ V_d+ V_e) /5
=> V_o = (V_a + V_b+ V_c+ V_d+ V_e).

3. Find the value of V₁ in the circuit shown below?

A. 4v
B. 2v
C. 3v
D. None of the mentioned
Answer: D
Clarification: Using the superposition theorem the voltage V₁ at non-inverting terminal is V₁ = V_a/4 + V_b/4+ V_c/4+ V_d/4 = [V_a + V_b+ V_c+ V_d] /4 = [4+(-3v)+6v+(-1v) ] /4 = 1.5v.

4. If the gain of a non-inverting averaging amplifier is one, determine the input voltages if the output voltage, if the output voltage is 3v?
A. V₁ =6v ,V₂=3v and V₃=2v
B. V₁ =9v ,V₂=5v and V₃=-4v
C. V₁ =8v ,V₂=-6v and V₃=1v
D. V₁ =7v ,V₂=4v and V₃=-3v
Answer: D
Clarification: As the output voltage = Average of all input voltage = sum of input voltage /3
∴ sum of input voltage =3×3=9.
From the given option, the combination of input voltage 7v, 4v and -3v gives the value 9v.

5. In the circuit shown, supply voltage = ±15v, V_a= +3v , V_b= -4v , V_c= +5v, R= R₁= 1kΩ and R_F= 2kΩ. 741 op-amp has A= 2×10⁵ and R₁= 10kΩ. Determine the output voltage internal resistance of the circuit?

A. V_o ≅3v , R_iF=6.67MΩ
B. V_o ≅3v , R_iF= 7MΩ
C. V_o ≅3v , R_iF=9.2MΩ
D. V_o ≅3v , R_iF= 3.5MΩ
Answer: A
Clarification: The output voltage V_o= [1 + (R_F/R₁)] × [ (V_a+V_b+V_c/3)] = [1+(2kΩ/1kΩ)] ×[(3-4+5)/3]= 2.67 ≅ 3v.
Internal resistance of circuit, R_iF =R _i [A×R₁/ (R₁+ R_F)] = 100Ω×[(200000×1kΩ)/(1kΩ+2kΩ)]
=> R_iF= 6.67 MΩ.

6. Find the type of amplifier that cannot be constructed in differential configuration?
A. Summing amplifier
B. Scaling amplifier
C. Averaging amplifier
D. Subtractor
Answer: C
Clarification: In differential op-amp configuration, an amplifier produces sum or difference between two input terminals of op-amp. So, averaging is not possible in this type of configuration.

7. Calculate the output voltage, when a voltage of 12mv is applied to the non-inverting terminal and 7mv is applied to inverting terminal of a subtractor.
A. 19mv
B. 5mv
C. 1.7mv
D. 8.4mv
Answer: B
Clarification: Output voltage of a subtractor V_o = V_{non-inverting terminal} – V_{inverting terminal} = 12mv-7mv =5mv.

8. Find the differential amplifier configured as a subtractor from the given circuit.

Answer: D
Clarification: A basic differential amplifier is used as a subtractor when all the external resistors are equal in value.
The output voltage, V_o= -(R/R)×(V_a -V_b)
V_o= (V_a -V_b). Hence the circuit is called as subtractor.

9. How many additional sources are connected to each input terminal to obtain an eight input summing amplifier?
A. Six
B. Three
C. Four
D. Eight