Bipolar & Junction-Gate Transistors

Bipolar & Junction-Gate Transistors: BJT Physics: Injection Efficiency, Base Transport & the Gummel Plot, BJT Models (Ebers-Moll, Gummel-Poon) & Switching, JFET Physics: Channel, Pinch-off & the Shockley Equation.

• BJT Physics: Injection Efficiency, Base Transport & the Gummel Plot — Inside the bipolar transistor. Learn NPN/PNP structures and doping profiles, transistor action (emitter injection, base diffusion, collector collection), minority-carrier distributions in each region, emitter injection efficiency γ, base transport factor α_T, current gain α and β from physical parameters, the role of emitter bandgap narrowing, base-width modulation and the Early effect, collector multiplication, high-injection and the Kirk effect, the Gummel plot and β vs current, and temperature dependence — with Python computing γ, α_T, β, I_S, Early voltage and Kirk current from doping and geometry.
• BJT Models (Ebers-Moll, Gummel-Poon) & Switching — Modelling and switching bipolar transistors. Learn the Ebers-Moll model (injection and transport versions) valid in all regions, reciprocity (α_F I_ES = α_R I_CS), deriving V_CE(sat), the Gummel-Poon extensions (base charge, Early effect, high injection, low-current recombination) used in SPICE, charge-control modelling, the hybrid-π small-signal model with g_m, r_π, r_o, C_π (diffusion + junction) and C_µ, f_T and f_max, and switching behaviour: delay, rise, storage and fall times, overdrive, Baker clamps and Schottky transistors — with Python computing V_CE(sat) vs forced β and storage/rise times.
• JFET Physics: Channel, Pinch-off & the Shockley Equation — The junction field-effect transistor from the inside. Learn N- and P-channel construction, the gate PN junction controlling channel thickness, depletion from gate voltage and drain voltage, pinch-off and current saturation, the internal pinch-off voltage V_P0 = qN_Da²/(2ε), V_GS(off), I_DSS and open-channel conductance, the Shockley square-law approximation, output and transfer characteristics, small-signal g_m, r_o and capacitances, low-noise and high-input-impedance properties, temperature behaviour (zero-TC point) and applications — with Python deriving pinch-off voltage, I_DSS, I_D and g_m from doping and geometry.