Semiconductor Fundamentals

Atoms, bands, junctions and transistors. Where every chip starts: silicon crystals, energy bands, doping and carriers, the p-n junction, diodes, bipolar transistors and FETs, and the physics and models of the MOSFET that every VLSI design is built from.

• Semiconductor Physics — Every chip starts with the physics of silicon. Learn energy bands and the band gap, intrinsic carriers, doping with donors and acceptors, electron and hole concentrations (n·p = nᵢ²), the Fermi level, drift and diffusion currents, mobility and the Einstein relation, conductivity, and how temperature changes it all — with a calculator for doped silicon.
• Diodes & the PN Junction — The diode is the simplest semiconductor device — a one-way valve for current. Learn doping and the PN junction, forward and reverse bias, the Shockley equation and 0.6–0.7 V drop, I–V characteristics, diode types (signal, Schottky, LED, photodiode, varactor), and practical uses such as LED current limiting and reverse-polarity protection.
• Bipolar Junction Transistors (BJT) — The BJT amplifies current: a small base current controls a large collector current. Learn NPN/PNP structure, operating regions (cut-off, active, saturation), current gain β, voltage-divider biasing, DC operating point (Q-point), transconductance, and the BJT as a switch and amplifier.
• MOSFETs & JFETs — Field-effect transistors are voltage-controlled: the gate voltage sets the channel current with almost no gate current. Learn JFET and MOSFET structure, enhancement vs depletion, N- vs P-channel, threshold voltage, square-law and triode regions, transconductance, R_DS(on) switching, gate charge and logic-level drive.
• MOSFET Device Physics & Models — The MOSFET is the building block of every digital and analog chip. Learn the MOS capacitor, inversion and threshold voltage, the cut-off/triode/saturation regions, the square-law I–V equations, channel-length modulation, body effect, subthreshold conduction, velocity saturation and short-channel effects, and why FinFETs and nanosheets replaced planar transistors.