New simplest PWM generator WITHOUT 555 timer IC (improved version using ONLY transistors!!)
Published at : 23 Dec 2025
Ever since I made a video about my transistor based PWM circuit that doesn't need a microcontroller nine months ago, it bugged me that the circuit only worked with a MOSFET to switch the load, not just another simple transistor. After all the idea behind the whole thing was to avoid any fancy extra components like the 555 timer in favor of parts that can easily be salvaged from e-waste, so being quite a bit rarer than transistors, MOSFETs would definitely better be optional not obligatory. Luckily while designing the circuit for my DIY soldering station I figured out a way to make it work with transistors only - But alas! Another much newer channel beat me to it, and to my dismay his solution was even better than mine! So in this video we analyze both versions of the circuit and take the best of each to create one hopefully perfect PWM generator!
And here the schematics: it's worth noting that I did a couple errors calculating the resistors originally, so all the versions you can download below are recalculated and revised, thats why there is now only one value per component. You still have some leeway, but if you want to use other transistors than direct equivalents you'll need to change some resistor values to accommodate the current gain of those specific transistors.
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