VH >= VL

why not use the lower output to pull one of the upper inputs up or down instead?

NT

Through a diode? I don't want the diode drop.

This can also be done with a comparator and a mux, with glitches.

Ay yay yay. I saved 15% on car insurance

Done it a long time ago,

Various solutions for varying levels of precision and speed. None that are elegant (i.e., two diff input stages married to a common gain stage), just a very tiny selection of video limiter amps for $$$.

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website:

I suppose you could compensate with a diode drop on the Vl line too, matching diode currents, but it's more complex. Don't you run into issues with psu voltage lower limits on your opamp?

NT

This one

is a simplified version of the classic closed-loop ideal rectifier/clamp. The old ones usually had more parts to keep the opamp from winding up when railed, but modern RRIO amps come out of saturation very well. There are tiny glitches around the opamp slews, but they won't bother me in my gadget.

that's a dropless rectifier stage. I'm not seeing how that solves the issue of Vh opamp getting V_Psu that can go all the way down to nothing. Presumably the voltages in your system don't enable that situation to happen.

NT

It keeps OUT from going below VL.

I just don't want the processed VH to go below VL. That could blow out parts in my pulse generator output stage.

The outputs of this little clamp thing go to some biggish amps that drive the real power rails of my output stage. Those amps have gain, so the limiter circuit has to be fairly precise.

Sure it's simple. It sometimes takes a lot of engineering to make things simple.

Getting a resistive divider right does require attention to detail. I don't put my signature and date every time I use one.

those were clear from the start. I can only presume your rails are such that what I mentioned doesn't occur.

yep :)

NT

When you do as many sims as we do, we put a title, engineer's name, and date on every one. Even dumb ones. We must have thousands now, and we need to keep organized.

All our drawings and whiteboard pics have title blocks too. We even include that sort of stuff in software!

fair enough..just ribbing you a little. A process is a good thing

It's hard to tell, on usenet, what's going on. Irony doesn't transmit well over fiber cables.

On my possibly futile and useless pulse generator project, one three-transistor Spice circuit is T577_out_28.asc, which is the 28th saved iteration of one little circuit. And I don't spin the number for trivial edits. #28 got Gerbered for some test boards.

We have what I think is a nice process for PCB layouts too. It synchronzes schematics, pcb layouts, and PADS ECOs (which convey schematic changes into the PCB) throughout a board development.