Week 09
Active Filters
I study differential stages, feedback, filters, and output stages as one connected signal path.
What I connect in this unit
An active filter combines an op-amp with an RC network for low-pass or high-pass response. Two energy-storage elements create a second-order denominator whose quality factor sets peaking and damping near cutoff.
Concept map
- Low-pass response
- High-pass response
- Second-order response
- Quality factor
Technical anchor
For H(s) = Kω0²/(s² + (ω0/Q)s + ω0²), a second-order Butterworth low-pass uses Q = 1/√2.
How I review it
Choose R and C ratios from target f0 and Q, then check DC gain, magnitude at f0, and the eventual −40 dB/dec slope against the design equation.
Connection to the full course
Unit 9 of 12. Unit numbers follow concept dependencies rather than the historical lecture calendar.