Topic: Electronic Devices
Match the following regions of a noise spectrum (Relative Amplitude vs Frequency) to their dominant noise types:
A: Low frequency region
B: Spikes at mains frequency
C: Spikes at high switching frequencies
D: Flat wideband noise floor
- A. A: Thermal Noise, B: Power line pick up, C: Power supply switching noise, D: 1/f noise
- B. A: Power line pick up, B: Thermal Noise, C: 1/f noise, D: Power supply switching noise
- C. A: 1/f noise, B: Power line pick up, C: Power supply switching noise, D: Thermal Noise
- D. A: Power supply switching noise, B: 1/f noise, C: Power line pick up, D: Thermal Noise
Answer: C. A: 1/f noise, B: Power line pick up, C: Power supply switching noise, D: Thermal Noise
Explanation: In a typical noise spectrum: Region A at very low frequencies corresponds to 1/f noise (flicker noise). Region B consists of narrow spikes typically at 50/60 Hz and harmonics, caused by power line pick up. Region C contains higher frequency spikes caused by power supply switching circuits. Region D is the wideband, flat noise floor known as Thermal (Johnson) noise.