AC square wave

AC square wave from two 18650 batteries.
CORRECTION the capacitor on pin 2 connects to -3.7V not ground.
Link to notes: https://drive.google.com/file/d/1eZ940jAAwmdlNoTZnuD4ULv0CuXbLdNh/view?usp=sharing

Видео AC square wave канала Chris's Workbench