25. 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
In a non-inverting averaging amplifier, the non-inverting input voltage is the average of all inputs, with a positive sign.
26. Expression for output voltage of non-inverting summing amplifier with five input voltage?
A. Vo = 5×( Va + Vb+ Vc+ Vd+ Ve)
B. Vo = [1+( Rf/R1)]× ( Va + Vb+ Vc+ Vd+ Ve)
C. Vo = Va + Vb+ Vc+ Vd+ Ve
D. Vo = ( Va + Vb+ Vc+ Vd+ Ve) /5
Answer: C
The output voltage of the non-inverting summing amplifier is (1+ ( Rf / R1 )) times the average of all input voltages in the circuit.
Since there are five input voltages => (1+ ( Rf / R1 )) =5
Therefore, Vo = 5 × ( Va + Vb+ Vc+ Vd+ Ve) /5
=> Vo = (Va + Vb+ Vc+ Vd+ Ve).
27. Find the value of V1 in the circuit shown below?
A. 4v
B. 2v
C. 3v
D. None of the mentioned
Answer: D
Using the superposition theorem the voltage V1 at non-inverting terminal is
V1 = Va/4 + Vb/4+ Vc/4+ Vd/4
= [Va + Vb+ Vc+ Vd] /4
= [4+(-3v)+6v+(-1v) ] /4 = 1.5v.
28. 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
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.
29. In the circuit shown, supply voltage = ±15v, Va= +3v , Vb= -4v , Vc= +5v, R= R1= 1kΩ and RF= 2kΩ. 741 op-amp has A= 2×105 and R1= 10kΩ. Determine the output voltage internal resistance of the circuit?
A. Vo ≅3v , RiF=6.67MΩ
B. Vo ≅3v , RiF= 7MΩ
C. Vo ≅3v , RiF=9.2MΩ
D. Vo ≅3v , RiF= 3.5MΩ
Answer: A
The output voltage
Vo= [1 + (RF/R1)] × [ (Va+Vb+Vc/3)]
= [1+(2kΩ/1kΩ)] ×[(3-4+5)/3]= 2.67 ≅ 3v.
Internal resistance of circuit, RiF =R i [A×R1/ (R1+ RF)] =
100Ω×[(200000×1kΩ)/(1kΩ+2kΩ)]
=> RiF= 6.67 MΩ.
30. 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
In differential op-amp configuration, an amplifier produces the sum or difference between two input terminals of the op-amp. So, averaging is not possible in this type of configuration.
31. 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
Output voltage of a subtractor
Vo = Vnon-inverting terminal – Vinverting terminal
= 12mv-7mv =5mv.
32. 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
Answer: B
An eight-input summing amplifier can be constructed using a basic differential amplifier if six additional input sources are used by connecting three input sources to inverting and non-inverting input terminals through resistors.
33. Calculate the output voltage for the summing amplifier given below, where R=2kΩ and RL =10kΩ.
A. 4v
B. 18v
C. 8v
D. None of the mentioned
Answer: A
The output voltage for summing amplifier is given
Vo =-Va -Vb +Vc +Vd
=3-4+6+5 =4v.
34. The output voltage of a summing amplifier is equal to (assume the sum of input voltage as Vn )
A. V (non-inverting terminal)+ Vn (inverting terminal)
B. Vn (non-inverting terminal)+ (-Vn (inverting terminal)
C. -Vn (non-inverting terminal)+ (-Vn (inverting terminal)
D. -Vn (non-inverting terminal)+ Vn (inverting terminal)
Answer: B
The output voltage of the summing amplifier is equal to the sum of the input voltage applied to the non-inverting terminal plus the negative sum of the input voltage applied to the inverting terminal.
35. Strain gauge is an example of which device?
A. Transducer
B. Voltage follower
C. Integrator
D. Differentiator
Answer: A
A strain gauge is a device when subjected to pressure or force undergoes a change in its resistance.
36. An instrumentation system does not include
A. Transducer
B. Instrumentation amplifier
C. Automatic process controller
D. Tester
Answer: D
Except for the tester, the remaining blocks form the input, intermediate, and output stages of the instrumentation system.
37. Transmission lines are used for
A. Output signal
B. Input signal
C. Signal transfer
D. All of the mentioned
Answer: C
Transmission lines are the connecting line between the blocks and permit signal transfer from unit to unit.
37. The length of the transmission lines are
A. Longer than 10 meters
B. Shorter than 10 meters
C. Equals to 10 meters
D. None of the mentioned
Answer: D
The length of the transmission lines depends primarily on the physical quantities being monitored and on system requirements.
38. Why output of the transducer is not directly connected to the indicator or display?
A. Low-level output is produced
B. High-level output is produced
C. No output is produced
D. Input is fed directly
Answer: A
Many transducers do not produce output with sufficient strength to permit their users directly. Therefore, the low-level output signal of the transducer needs to be amplified.
39. What are the features of an instrumentation amplifier?
A. Low noise
B. High gain accuracy
C. Low thermal and time drift
D. All of the mentioned
Answer: D
Instrumentation amplifiers are intended for precise low-level signal amplification because of the features mentioned.
40. What is the disadvantage of using LH0036 instrumentation op-amp?
A. Extremely stable
B. Relatively expensive
C. Accurate
D. All of the mentioned
Answer:b
LH0036 is a very precise special-purpose circuit in which most electrical parameters are minimized and performance is optimized. So, it is relatively expensive.
