Week 05
Negative Feedback
I study differential stages, feedback, filters, and output stages as one connected signal path.
What I connect in this unit
Negative feedback subtracts a fraction of output from input, creating loop gain Aβ. Large loop gain makes closed-loop gain depend mainly on β, reduces sensitivity to device variation, and extends bandwidth.
Concept map
- Loop gain
- Closed-loop gain
- Sensitivity
- Bandwidth extension
Technical anchor
Closed-loop gain is Af = A/(1 + Aβ); when Aβ ≫ 1, Af ≈ 1/β and gain sensitivity falls by approximately 1/(1 + Aβ).
How I review it
Calculate gain change for a ±20 percent variation in A before and after feedback, then estimate the new bandwidth using a constant gain-bandwidth product.
Connection to the full course
Unit 5 of 12. Unit numbers follow concept dependencies rather than the historical lecture calendar.