==== Astable Multivibrator ====
=== 2 transistor ===
  * https://www.homemade-circuits.com/transistor-astable-multivibrator-amv-calculator/
  * https://rayshobby.net/wordpress/learning-electronics-1-multivibrator/
  * [[https://everycircuit.com/circuit/6145859360260096/astable-multivibrator---multivibratore-astabile-|simulated]]
  * https://www.electronics-tutorials.ws/waveforms/astable.html