BJT & MOSFET Amplifiers — Biasing & Small-Signal Models

Engineering

Advanced 120 minutes 2 lessons

PhD-level analysis of bipolar junction transistor (BJT) and MOSFET amplifiers: DC bias analysis using the Thevenin voltage-divider equivalent, small-signal hybrid-π and T models, mid-band gain derivation, and frequency response including Miller capacitance and the short-circuit current-gain bandwidth product f_T.

Learning Objectives

Compute the Q-point (I_C, V_CE) of a BJT voltage-divider bias circuit using exact and approximate methods
Derive the small-signal hybrid-π parameters g_m, r_π, r_o from the DC operating point
Compute mid-band voltage gain, input resistance, and output resistance of common-emitter and common-source stages
Apply the Miller effect to estimate the dominant high-frequency pole introduced by the collector–base capacitance C_μ
Calculate the MOSFET threshold voltage, overdrive voltage, and transconductance from device parameters