1. 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.
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
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.
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
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.
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
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.
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
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.
6. A LM307 amplifier has an 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
Answer: C
20log(1/SVRR) = 92dB
=> log(1/SVRR) = 92/20
=> 1/SVRR= 104.6
=> SVRR = 1/104.6 = 25.12µV/V.
7. Which value remains 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
Answer: D
△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 a 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 a 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
Answer: B
The SVRR = 15.85µV/V
for LM307 because of poor filtering and △V= 10mVrms.
9. What makes the output voltage equal to zero in practical op-amp?
A. Input offset voltage
B. output offset voltage
C. Offset minimizing voltage
D. Error voltage
Answer: A
The input offset voltage is the differential input voltage that exists between two input terminals of an op-amp without any external input and forces the output voltage to zero.
10. What happens due to a mismatch between two input terminals in an op-amp?
A. Input offset voltage
B. Output offset voltage
C. Bothe the input and output offset voltage
D. None of the mentioned
Answer: B
The input offset voltage in op-amp force the output voltage to zero due to the mismatch between two input terminal, there will be voltage produced at the output, and this voltage is called output offset voltage.
