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??)

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.

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.

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.