Total Output Offset Voltage MCQ [Free PDF] – Objective Question Answer for Total Output Offset Voltage Quiz

11. A completely compensated inverting amplifier is nulled at room temperature 25oC, determine the temperature at which the total output offset voltage will be zero?

A. 50oC
B. 25oC
C. 75oC
D. 125oC

Answer: B

When an amplifier is nulled at room temperature, the effect of input offset voltage and current is reduced to zero.

Change in the total output offset voltage occurs only if there is any change in the value of Vio and Iio. Therefore, the total output offset voltage will be zero at room temperature.

 

12. How the effect of voltage and current drift on the performance of an amplifier is determined?

A. △VooT/△T = {[1-RF/R1)]×(△Vio/△T)} + RF×(△Iio/△t)
B. △VooT/△T = {(-RF/R1)×(△Vio/△T)} + RF×(△Iio/△t)
C. △VooT/△T = {[1+(RF/R1)]×(△Vio/△T)} + RF×(△Iio/△t)
D. None of the mentioned

Answer: C

As the amplifier is used in inverting configuration, the effect of voltage and current drift is given as, the average change in total output offset voltage per unit change in temperature.

△VooT/△T = {[1+(RF/R1)]×(△Vio/△T)} + RF×(△Iio/△t).

 

13. The error voltage in a compensating inverting amplifier is obtained by

A. Multiplying △T to total output offset voltage
B. Multiplying △T to input offset voltage
C. Multiplying △T to input offset current
D. All of the mentioned

Answer: A

The maximum possible change in the total output offset voltage △VooT results from a change in temperature △t.

Therefore, the error voltage is obtained by multiplying △T by the average total output offset voltage.

Ev =( △VooT/△T)×△T = [1+(RF/R1)]×(△Vio/△T)×△T + RF×(△Iio/△T)×△T.

 

14. A 7.5kΩ internal resistor and a 12kΩ feedback resistor are connected to an inverting amplifier. Find the error voltage, if the output voltage is 3.99mv for input of 1.33mv.

A. ±0.6v
B. ±0.6mv
C. ± 60mv
D. ±6mv

Answer: D

The output voltage of inverting amplifier is

Vo= -(RF/R1)×Vin±Ev

=> Ev= ± Vo+(RF/R1)×Vin

= 3.99mv+(12kΩ/7.5kΩ)×1.33mv

= ±6.118 ≅ ±6mv.

 

15. Consider the amplifier is nulled at 27oC. Calculate the output voltage , if the input voltage is 6.21mv dc at 50oC. Assume LM307 op-amp with specification:

△Vio/△T=30µV/oC ; △Iio/△T = 300pA/oC; VS =±15v.

drift q7

A. +0.53v or -0.68v
B. +0.52v or -0.78v
C. +0.54v or -0.90v
D. +0.51v or -0.86v

Answer: D

Change in temperature △T = 50oC-27oC = 23oC.

=> Error voltage

Ev =[1+(RF/R1)]×(△Vio/△T)×△T + RF×(△Iio/△T)×△T

= [1+(100kΩ/1kΩ)] × (30µv/1oC × 23oC + 100kΩ × (300pA/1oC × 23oC = 0.06969 + 6.9×10-9

=> Ev= 0.0704 = 70.4mv.

For an input voltage of 6.21mv dc, the output voltage,

Vo=-(RF/R1)×Vin±Ev

= -(100kΩ/1kΩ) × 6.21mv ± 70.4mv

= +0.69v or -0.55v.

 

16. Which factor affects the power supply voltages in the amplifier?

A. Poor regulation and filtering
B. Resistive network connected to an amplifier
C. Change in temperature
D. All of the mentioned

Answer: A

A poorly regulated power supply gives different values depending on the size & type of load connected to it and a poorly filtered power supply has a ripple voltage riding on some specific dc level.

 

17. Change in the input bias current does not affect?

A. Input offset voltage
B. Output offset voltage
C. Input offset current
D. Output offset current

Answer: C

Even though the input bias currents change due to the change in supply voltages, the input offset current remain relatively constant because it is the absolute value of the difference between two input bias currents.

 

18. A supply voltage rejection ratio of 15µv/v is given for an op-amp. Find its equivalent value in decibels

A. 74db
B. 77dB
C. 76.48dB
D. 76dB

Answer: C

Supply voltage rejection ratio, SVRR in dB

= 20log(1/SVRR) =20log[1/(△Vio/△V)]

= 20log(1/150µV/V)

=20log(106/150)

=20log(6666.67) = 76.48dB.

 

19. When does the op-amp perform better?

A. Low value of SVRR in µV/V
B. High value if SVRR in µV/V
C. Low value of SVRR in dB
D. High value of SVRR in dB

Answer: A

The total value of SVRR in µV/V should be zero. The lower the value of SVRR in µV/V, the better will be the op-amp performance.

 

20. Write the equation for change in the output offset voltage?

A. △Voo = [-RF/R1)]× [△Vio/△V] ×△V
B. △Voo = [1+(RF/R1)]× [△Vio/△V] ×△V
C. △Voo = [1+(RF/R1)]× [△Vio/△V].
D. None of the mentioned

Answer: B

The change in the input offset voltage is given as

△Voo =[1+(RF/R1)]× [△Vio/△V] × △V

Where

△V = Change in supply voltage +Vcc & -Vee,

△Vio/△V = Supply voltage rejection ratio (µV/V) and

[1+(RF/R1)] = Gain of the differential amplifier.

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