As it turns out, the ever-useful 555 timer chip does the job admirably. It’s a simple enough circuit, the threshold pin is pulled high so the output goes high, and the PWM drive from an Arduino ...

With a little work, you could probably adapt this idea to any number of circuits out of the 555 playbook, like a PWM generator, for example. There’s almost nothing a 555 can’t do. If you want ...