Week 08
Common-Emitter Amplifiers
I organize a study path from diodes to single-transistor amplifiers in the order that makes the circuit behavior easiest to revisit.
What I connect in this unit
A common-emitter stage produces phase inversion because collector voltage falls as collector current rises. Coupling capacitors isolate DC bias, and an emitter bypass capacitor removes AC degeneration to increase midband voltage gain.
Concept map
- Voltage gain
- Phase inversion
- Coupling capacitors
- Bypass capacitors
Technical anchor
With an effective bypass, Av ≈ −gmRC; without it, Av ≈ −gmRC/(1 + gmRE), showing the gain reduction from emitter feedback.
How I review it
Compare input and output midband waveforms for inversion, then calculate the resistance seen by each coupling and bypass capacitor to locate its low-frequency pole.
Connection to the full course
Unit 8 of 12. Unit numbers form a concept-study sequence and do not claim the original class schedule.