Re: gEDA-user: Opamps et al...

[Peter Clifton <pcjc2@xxxxxxxxx>]

On Tue, 2006-11-21 at 06:24 -0500, Stuart Brorson wrote:
> On Tue, 21 Nov 2006, Peter Clifton wrote:
> > The intended application is a current shunt amplifier to sense the load
> > current of a chunky MOSFET + resistor bank.
> 
> Why not just use one of the current generation of high-side current
> sensing ICs?  For example:
> 
> http://www.linear.com/pc/viewCategory.do?navId=H0,C1,C1154,C1009,C1077
> http://www.analog.com/en/subCat/0,2879,759%255F777%255F0%255F%255F0%255F,00.html

Simply ignorance.. I didn't know such beasts existed. They look
interesting, however I've gone for the Instrumentation amp for now. (I
looked up a few of the promising part numbers from our main supplier,
and they aren't available. I would have to hunt them down or order
samples).

> Or even:
> 
> http://www.national.com/pf/LM/LM3822.html

Those look nice for small stuff, but I'm doing 40A+... need an external
shunt.

> The folks at ADI, Linear Tech, National and so on have already solved
> this problem many times.  Their solutions may be better than yours
> (although not as much fun as rolling your own).  In any event, if you
> just want to slap  something onto FR-4 and get on with it, this may be
> the best approach.

Indeed.. I'm always amazed when I read their App notes. There are some
really ingenious (/devious) circuits. I like to show caution when
looking at them though, as they often use numerous of the companies
(often expensive) chips, and they can be hard to get hold of. Sometimes
the ideas and topologies, are transferable to "standard" chips though.

Thanks for the links,

Peter C



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