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Practice Sheet 1

The document presents a series of practice problems related to operational amplifiers (opamps) and their applications in various types of voltmeters, including difference amplifiers, voltage followers, and rectifiers. Each problem includes specific resistor values, input voltages, and the required calculations for differential gain, common mode gain, output voltage, and other parameters. The answers for each problem are provided, showcasing the calculations needed to achieve full-scale deflection (FSD) for the respective configurations.

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sayaksardar04
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30 views4 pages

Practice Sheet 1

The document presents a series of practice problems related to operational amplifiers (opamps) and their applications in various types of voltmeters, including difference amplifiers, voltage followers, and rectifiers. Each problem includes specific resistor values, input voltages, and the required calculations for differential gain, common mode gain, output voltage, and other parameters. The answers for each problem are provided, showcasing the calculations needed to achieve full-scale deflection (FSD) for the respective configurations.

Uploaded by

sayaksardar04
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Practice Problem

1. Consider the difference amplifier with R1 = R3 = 10 kΩ and R2 = R4 = 1 MΩ. Given inputs are
vI2 = 5.005 V and vI1 = 4.995 V. Assume opamp is ideal.
a. Find the values of differential gain (Ad), common mode gain (Acm), corresponding CMRR, and
output voltage (vO).
b. Find the values of differential input resistance Rid and output resistance RO.
c. If resistors have 2% tolerance (i.e., each can vary by ±2% of its normal value, and the worst-
case mismatch between R1 & R3 is 4%, and between R2 & R4 is 4%), find the value of the worst-
case common mode gain (Acm), the corresponding value of CMRR, and the output voltage (vO).
[Ans: a), Ad = 100, Acm = 0, CMRR = infinite, vO = 1 V; b), Rid = 20 kΩ, RO = 0; c), |Acm|=
82.44x10-3 V/V, CMRR = 1213.003, vO = 0.588 V]

2. An opamp voltage-follower dc voltmeter has Ra = 800 kΩ, Rb = 100 kΩ, Rc = 60 kΩ, and Rd =
40 kΩ. A 100 µA FSD (full scale deflection) meter is used with a coil resistance of Rm = 1 kΩ.
Determine the Rs resistance to give FSD when input voltage E is 10 V and the knob switch is
connected to ‘C’ position. Find the input voltage E to give FSD for switch connections to ‘A’,
‘B’ and ‘D’ positions.
[Ans: Rs = 9 kΩ; For ‘A’, ‘B’ and ‘D’ switch positions, E values to give FSD are 1 V, 5 V, and
25 V, respectively.]
3. An opamp amplifier dc voltmeter uses a 100 µA FSD (full scale deflection) meter with a coil
resistance of Rm = 10 kΩ. Determine suitable values of resistances R3 and R4 to give FSD when
the input voltage E is 50 mV. Assume, R3 + R4 = 1 kΩ.
[Ans: R3 = 50 Ω; R4 = 950 Ω]

4. An opamp voltage-to-current converter dc voltmeter uses a 100 µA FSD (full scale deflection)
meter with a coil resistance of Rm = 1 kΩ. If R3 = 100 kΩ, determine the values of input voltage
E to give FSD and 0.5 FSD.
[Ans: For FSD, E = 10 V; For 0.5 FSD, E = 5 V]
5. An opamp half-wave rectifier ac voltmeter uses a 500 µA FSD (full scale deflection) meter with
a coil resistance of Rm = 560 Ω. If Rs = 440 Ω, calculate the rms input voltage Erms required to
give FSD.
[Ans: For FSD, Erms = 1.111 V]

6. An opamp half-wave rectifier ac voltmeter uses a 100 µA FSD (full scale deflection) meter with
a coil resistance of Rm = 10 kΩ. If R3 = 50 Ω, R2 = 950 Ω, calculate the rms input voltage Erms
required to give FSD.
[Ans: For FSD, Erms = 111.07 mV]
7. An opamp half-wave rectifier ac voltmeter uses a 500 µA FSD (full scale deflection) meter with
a coil resistance of Rm = 560 Ω. If R3 = 440 Ω, calculate the rms input voltage Erms required to
give FSD.
[Ans: For FSD, Erms = 488.72 mV]

8. An opamp full-wave rectifier ac voltmeter uses a 500 µA FSD (full scale deflection) meter with
a coil resistance of Rm = 560 Ω. If R3 = 440 Ω, calculate the rms input voltage Erms required to
give FSD.
[Ans: For FSD, Erms = 244.36 mV]

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