Generate pwm using ic 555
From wikiluntti
Introduction
IC 555 is an astable oscillator (vibrator).
Frequency:
Theory
Method 1
Method 2: with diodes
555 internal design and theory
For more details, see this:
and the internal circuit looks like below:
References
https://www.homemade-circuits.com/how-to-use-ic-555-for-generating-pwm/
