Filters & Frequency Behavior#

Shaping signals in time and frequency. Every analog circuit has a frequency response — intentional or not. Filters make that response deliberate: passing some frequencies, rejecting others, and defining the bandwidth of a signal path.

Understanding frequency behavior also means understanding what happens outside the passband — the roll-off, the phase shift, and the unintended resonances that turn a clean design into an oscillator.

What This Section Covers#

• RC & RL Filters — Low-pass, high-pass, and band-pass intuition with passive components.
• Active Filters — Op-amp-based filter designs, stability, and component sensitivity.
• Frequency Response — Gain vs. frequency, phase, roll-off, Bode plots, and unintended behavior.