PWM, "another hobby level transistor design lesson"

Hi,
Here is another hobby level transistor circuit design,
I went through my course design books looking at the formulas for designing a schmitt trigger circuit, and it explained well all the design equations for the collector,emitter and base to ground resistor, for the output transistor.
However, when it came to the feedback resistor and the collector resistor for the input transistor, they just setup some formulas, to implement into equations.
They said that, to derive the equations would take a long and tedious process, involving simultaneous equations for both upper and lower threshold voltages, during all conditions, so they were going to avoid teaching, as it involves more than what is necessary to design this circuit.

I like to be able to design a transistor circuit, where I know why each component needs to be in it, and how to calculate the values for those components.

So this video is a watered down version of designing a voltage level detector circuit, that any novice can understand at a hobby level. As well as have the circuit actually work very well for the purpose it was designed for. I demonstrate the "pulse width modulation" function of it using my osilloscope, to show the waveforms.

enjoy



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thanks.