Electronics 01
How to Calculate Crystal Load Capacitors (With Stray C)
CL = C1·C2/(C1+C2) + Cstray, but which stray? Worked 18 pF example, the ppm error from getting it wrong, and the gain margin check most guides skip.
oscillators
Electronics 02
555 Timer Frequency Formula: Where 1.44 Comes From
f = 1.44/((R1 + 2R2)C). Why 1.44 is 1/ln 2, why duty cycle can't drop below 50%, and why the diode fix misses 50% at 5 V. Worked 1 kHz example.