Explain thermal noise and shot noise in electronic circuits.

Thermal noise (Johnson-Nyquist) is generated by random thermal motion of charge carriers in resistive elements: Vn = sqrt(4kTRB) where k is Boltzmann constant, T is temperature, R is resistance, B is bandwidth. Shot noise occurs due to discrete nature of charge carriers in semiconductor junctions: In = sqrt(2qIB) where q is electron charge and I is DC current. Both are white noise (flat spectrum). Minimizing noise requires low-impedance design, cooling, proper bandwidth limiting, and selection of low-noise components.