Noise In Electronic Circuits multiple choice questions

Posted by -

 Noise In Electronic Circuits

1. If the amplifier is sold to engineering public, the noise figure that would be quoted in a catalog is
 a) 0.46
b) 0.94
c) 1.83
d) 2.93
Answer: 1.83
2. Noise factor for a system is defined as the ratio of
a) Input noise power (Pni) to output noise power (Pno)
b) Output noise power (Pno) to input noise power (Pni)
c) Output noise power (Pno) to input signal power (Psi)
d) Output signal power (Pso) to input noise power (Pni)
Answer: Output noise power (Pno) to input noise power (Pni)
3. What is the maximum average effective input noise temperature that an amplifier can have if its average standard noise figure is to not exceed 1.7?
 a) 203 K
b) 215 K
c) 235 K
d) 255 K
Answer: 203 K
4. A receiver is operated at a temperature of 300 K. The transistor used in the receiver have an average output resistance of 1 k. The Johnson noise voltage for a receiver with a bandwidth of 200 kHz is
 a) 1.8 µV
b) 8.4 µV
c) 4.3 µV
d) 12.6 µV
Answer: 1.8 µV
5. The noise voltage (Vn) and the signal bandwidth (B) are related as
a) Vn is directly proportional to bandwidth
b) Vn is directly proportional to √bandwidth
c) Vn is inversely proportional to absolute temperature
d) Vn is inversely proportional to bandwidth
Answer: Vn is directly proportional to √bandwidth
6. A mixer stage has a noise figure of 20 dB. This mixer stage is preceded by an amplifier which has a noise figure of 9 dB and an available power gain of 15 dB. The overall noise figure referred to the input is
 a) 11.07
b) 18.23
c) 56.43
d) 97.38
Answer: 11.07
7. In a receiver the input signal is 100 V, while the internal noise at the input is 10 V. With amplification the output signal is 2 V, while the output noise is 0.4 V. The noise figure of receiver is
 a) 2
b) 0.5
c) 0.2
d) None of the mentioned
Answer: 2
8. If a matched attenuator with a loss of 3.2 dB is placed between the source and the amplifier’s input, what is the operating spot noise figure of the attenuator amplifier cascade if the attenuator’s physical temperature is 290 K?
 a) 9 db
b) 11.3 db
c) 10.4 db
d) 13.3 db
Answer: 13.3 db
9. What average operating noise figure results when the amplifier is used with an antenna of temperature 30 K?
 a) 9.54 db
b) 10.96 db
c) 11.23 db
d) 12.96 db
Answer: 9.54 db
10. A resistor R 1 k is maintained at 17C. The rms noise voltage generated in a bandwidth of 10 kHz is
 a) 16 x 10^(-14) V
b) 0.4 µV
c) 4 µV
d) 16 x 10^(-18) V
Answer: 0.4 µV
11. A system has three stage cascaded amplifier each stage having a power gain of 10 dB and noise figure of 6 dB. the overall noise figure is
 a) 1.38
b) 6.8
c) 4.33
d) 10.43
Answer: 4.33
12. Noise Factor(F) and Noise Figure(NF) are related as
a) NF = 10 log10(F)
b) F = 10 log10(NF)
c) NF = 10 (F)
d) F = 10 (NF)
Answer: NF = 10 log10(F)
13. Which type of noise is produced when the op-amp has wider bandwidth?
 a) 1/f noise
b) Schottky noise
c) Thermal noise
d) Radiant noise
Answer: Schottky noise
14. How to choose an IC for a high electrical noise environment?
 a) Low degree of noise immunity
b) High degree of noise immunity
c) Low degree of noise reduction
d) High degree of noise reduction
Answer: High degree of noise immunity
15. Which among the following is not a source of internal noise?
 a) AC random voltages generated within conductors
b) Lightning
c) Switching of circuits
d) None of the mentioned
Answer: Lightning
16. Which among the following has best immunity to induced noise?
 a) Non-inverting amplifier
b) Inverting amplifier
c) Differential amplifier
d) Voltage follower
Answer: Differential amplifier
17. The type of noise phenomena that increases with increase in temperature is
a) None of the mentioned
b) 1/f noise
c) Schottky noise
d) Thermal noise
Answer: Thermal noise
18. Mention a scheme to reduce the effect of electrical noise on ICs?
 a) Isolating ICs on different boards
b) Add a filter near ICs
c) Physical shielding of ICs
d) Use of compensating networks near ICs
Answer: Physical shielding of ICs
19. The major source of interference with the desired signal in electronic system is called
 a) Error signal
b) Interference signal
c) Noise signal
d) Faulty signal
Answer: Noise signal
20. Internal noise generation can be reduced by keeping
 a) None of the mentioned
b) Input lead length short
c) Both input and output lead length short
d) Output lead length short
Answer: Both input and output lead length short
21. The factors that determine the amount of noise induced is
 a) Type of coupling between two circuits
b) Rate of change of current per unit time
c) Speed of operation of circuit
d) All of the mentioned
Answer: Type of coupling between two circuits
22. Identify the external noise sources
 a) Switching of rotating machinery
b) Control circuits
c) Ignition system
d) All of the mentioned
Answer: Control circuits
23. The noise due to random behaviour of charge carriers is
a) Shot noise
b) Partition noise
c) Industrial noise
d) Flicker noise
Answer: Shot noise
24. The noise temperature at a resistor depends upon
a) Resistance value
b) Noise power
c) Both a and b
d) None of the above
Answer: Noise power
25. Noise is added to a signal in a communication system
a) At the receiving end
b) At transmitting antenna
c) In the channel
d) During regeneration of the information
Answer: In the channel

Comments

Post a Comment