18. Noise, Ch. 16, Senturia
Noise often limits performance of MEMS sensors and other devices (oscillators, filters, for example).
What we often think of as noise can be divided into 2 (or more) parts.
1. Interference.
2. Random noise.
3. Drift, aging effects… (random noise??)

19. Interference
Definintion: Unwanted sensitivity to external or internal disturbances.
Electrical, thermal, mechanical, optical…
Examples.
Electrical: Capacitive coupling to 60 Hz, radio waves, driving voltage to output …
Mechanical: Sensitivity to vibration…
Optical: Sensitivity to ambient light.
System design critical (Senturia has examples)
References: Keithley, Low-Level measurements + others.

20. Random Noise Thermal noise. Shot noise. Flicker noise (1/f noise).
Dissipative processes result in fluctuations.
Energy storage elements have a non-zero fluctuating amount of energy stored.
Shot noise.
Current consists of discrete particles.
Flicker noise (1/f noise).
Mostly capture and release of carriers from traps in electrical circuits. Many physical mechanisms, generally.

23. Thermal Noise
Statistical mechanics -> average energy of a particle = 3/2 kBT. (1/2 KBT for each degree of freedom (x, y, z))
Mass with 1 degree of freedom -> ½ kBT <-> inductor!
Inductor has on average ½ kBT of energy.
The capacitor is also an energy storage element with one degree of freedom. If connected to its environment with a resistor (or almost anything else) it has an average stored energy of ½ kBT! This does not depend on the size of the resistor or capacitor!
Spring (capacitor) also has ½ kBT.
This is characteristic of thermal noise.