# Linear Integrated Circuit Questions and Answers – Effect of Variation in Power Supply Voltage on Offset Voltage

This set of Linear Integrated Circuit Multiple Choice Questions & Answers (MCQs) focuses on “Effect of Variation in Power Supply Voltage on Offset Voltage”.

1. Which factor affects the power supply voltages in amplifier?
a) Poor regulation and filtering
b) Resistive network connected to amplifier
c) Change in temperature
d) All of the mentioned

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

2. 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

Explanation: 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.

3. 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

Explanation: 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.

4. 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

Explanation: 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.

5. 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

Explanation: 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.

6. A LM307 amplifier has SVRR of 92dB, express it in terms of microvolts per volts?
a) 65µV/V
b) 37.98µV/V
c) 25.12µV/V
d) 101.4µV/V

Explanation: 20log(1/SVRR)=92dB
=> log(1/SVRR) = 92/20
=> 1/SVRR= 104.6
=> SVRR = 1/104.6 =25.12µV/V.

7. Which value remain the same regardless of whether it is computed from the change in low dc supply or change in +Vcc or -Vee ?
a) △V
b) △Vio
c) △Voo
d) None of the mentioned

Explanation: △V value is the same regardless of whether it is computed from the change in low dc supply or change in +Vcc or -Vee . For example, suppose that -Vee remains constant at -10v then the +Vcc has to vary from 8 to 12v as a result of change in low dc voltage. This means that the change in △V in supply voltage +Vcc is 2v in either direction from 10v.

8. Consider LM307 is initially nulled. Suppose, the op-amp has poor filter, 20mVrms then ac ripple is measured across the terminals. If Vin=0v, determine the change in output offset voltage caused by the change in supply voltage?

a) 81µVrms
b) 8.1µVrms
c) 0.81µVrms
d) 810µVrms

Explanation: The SVRR =15.85µV/V for LM307 because of poor filtering and △V=10mVrms .
The change in output offset voltage, △Voo =[1+(RF/R1)]× [△Vio/△V] ×△V = [1+(950kΩ/1kΩ)] × (15.85µV/V) × 910mv= 8.1µVrms.

Sanfoundry Global Education & Learning Series – Linear Integrated Circuits.