Darlingtons
Posted: Sun Aug 22, 2010 9:16 amA useful array is the ULN200x series - this gives 7 darlingtons in one chip and switches to common ground.
Yes, I've used these to good effect in the past. More recently, I'm using logic level drive fets of various sorts for the same kind of jobs. One nifty example is using a IRF 7105 wired as a CMOS buffer with ampere level outputs for amplifying the PWM output from a microprocessor. I've used that (with an output filter L) to drive CCFL inverters and regulate their output via a feedback divider to an a/d input on the same chip -- works great, no fancy PID algorithm needed to give good stable HV for geigers and phototubes. This lashup is extremely efficient if a very small inductor is in the supply line to the fet pair to reduce shoot-through currents.
I also use some larger FETs with low thresholds to control "real" power -- 100's of amps and high volts. This may not be as fast as some bipolars, but is often fast enough, and also often faster than many darlingtons. IRL 3705 and 1104 are used here a lot for big things. Of course, it's hard to find LL fets that are also high voltage on the D-S, but those are the breaks the tech lets you have. They are such low on resistance that needing a heatsink means something is broken, very nicely efficient normally.