Part 2 · Voltage Regulation
Key point: dropping 12 V to 3.3 V with a series resistor can hit the voltage at one current — but load steps and efficiency kill it. A bulk cap only slows the failure.
12 V → \(R\) → 3.3 V · 10 µF · profile 100 → \(100{+}\Delta I\) → 100 → \(100{-}\Delta I\) · dwell ~6τ
\(V_{\mathrm{OUT}}\) · blue in-spec · red out · green = ±5% around 3.3 V
\(I_{\mathrm{LOAD}}\) · 100 mA → up → 100 mA → down
Circuit: stiff \(V_{\mathrm{IN}}\) → series \(R\) → node with current load + \(C\). After a current step, \(V\) exp-settles with \(\tau = RC\) toward \(V_{\mathrm{IN}}-IR\). Trace is red while outside ±5%.
Try it: default ΔI = 10 mA → sequence 100·110·100·90 mA. Watch a clean blue start at 3.3 V, then slow red excursions as \(V\) crawls with \(\tau=RC\). ΔI = 0 stays flat in-band — still dumps most power in \(R\).