how to design programmble slew rate control circuit for electronic load

Look up ramps and integrators, and think about current sources into capacitors.

I need the circuit by amplifier. thank you

Like I said, ahem: "Look up integrators." Include one inside your amplifier's feedback loop.

can you give me a sample circuit,thanks a lot

can you give me a sample circuit,thanks a lot

And the irony is, he's posting via Google. Maybe tragedy, eh?

Here's a simple gain-of-one circuit that follows an input control voltage, but with a programmable slew rate, using a programmable transconductance opamp.

. slew Vs Rs . rate o---/\\/\\---, Programmable Slew Rate . programming | by Winfield Hill . ,------------+ . | __ | Vs . '--|- \\ |/V S = ----- volts/sec . | >---| Rs Cs . gnd --|+_/ |\\ . | R . ,----- | ----/\\/\\-----, . | | Cs | . in R | ___| ,---||----+ R . o--/\\/\\--+--|+ \\ | __ | ,---/\\/\\---, . | >---+--|- \\ | R | __ | . gnd --|-__/ | >--+--/\\/\\--+--|- \\ | out . / gnd --|+_/ | >---+--o . / gnd --|+_/ . transconductance amp

Example of transconductance opamps are NSC's LM13700, the original CA3080 or NSC's copy, the LM3080. These are still available from surplus suppliers (I kept a lifetime supply). You could also try a Burr-Brown opa660 over a limited range.

You need an electronics BOOK. Paper with ink on it. A very thin, cheap, basic one.

robert

The heart of this circuit, and the key to its simplicity, is the transconductance amplifier. While these do indeed allow for an uncomplicated circuit, there are at least four other ways to solve the problem using conventional components, but they're decidedly more complex. I'm sorry to see venerable transconductance amplifiers headed for that fabled IC heaven in the sky, but that hasn't completely happened just yet. NSC reports their parts are in production and are stocked at Arrow, Future, and Newark. Well, the soic package at Newark, anyway.

I've got five bucks that says he comes back and asks for component values. ;-)

Cheers! Rich

Dood, have you seen the latest version of Google? They've really snazzed it up, and although the groups interface is still idiotic, they make it really easy for Joe Scriptkiddie to log in and post context-free posts.

Feh. Rich

Winfield hill,thanks, I am difficult to see ascii circuit,can you give me a jpg or other picture format circuit. send it to my email: snipped-for-privacy@gmail.com

Feh, indeed! I've no interest in gmail, although I do tip my hat to their brilliant marketing using artificial scarcity and "invitations."

I'd be content for the Google guys to spend a considerable portion of eternity in A Bad Place for their truly egregious treatment of the usenet as a subset of "Google Groups." Extra time added for the poor implementation, of course.

Set your viewer to a non-proportional font like Courier, or copy the text into an editor where you can view it.

I imagine he read your comment, so instead he came back asking for a jpg image by email. Could be a troll. boki?

Too much work. Could you please build it for him and then send it him. He'll pay for the components and as he understand you've passed some time building it, maybe he'll pay you a coffee too. Or two if he feels generous :-)

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Well, I guess that thing to do is not to use nonlinear parts if they cause too much nonlinearity. That's what engineering is all about. What engineering is *not* about is following stock rules.

The place resistor nonlinearity gets serious is precision high-voltage stuff, where it's a serious problem.

John

OTA is difficult to buy,and I have some conventional amp,so I hope use convertional amp to build it.I very need your help. email: snipped-for-privacy@gmail.com

They're much more complicated, you're better of with the ready-made programmable amplifier.