gEDA-user: furnace controller I/O port again

[Bob Paddock]

On Thursday 02 November 2006 12:51, DJ Delorie wrote:

> > Be sure to check how long it takes the op-amps to come out of
> > saturation if you intend to use this for high-speed signals.
> > Comparators (ones with totem-pole outputs) are usually better suited
> > to this application.
> 
> I'll look into it.  The thing about op amps is that they're cheap and
> tiny.

Which frequently gets people into trouble when they try to use
Op-Amps as Comparators:

Analog Devices:
"Issue 11:	Comparators & Op Amps – May They Never Meet
(Or Good Advice From Mr. Punch)	The Question: 
Why buy an expensive comparator when an op amp is just as good? 
Download this article  [pdf, 364,544 bytes]"
http://www.analog.com/en/content/0,2886,760%255F788%255F87112,00.html


TI:
Op Amps and Comparators - Don't Confuse Them

Operational amplifiers (op amps) and comparators look similar; they even have very similar schematic symbols. 
This leads a lot of designers to think they are interchangeable. There is a strong temptation to use a spare section 
of a multiple op amp package as a comparator to save money. This application note will explain why designers should not do this. 

http://encon.fke.utm.my/nikd/latest/sloa067.pdf
Download .pdf (sloa067.pdf, 150 Kbytes)"


To go along with the PDP-5, here are some Op-Amp notes from 1963 & 1966:
http://focus.ti.com/docs/apps/catalog/resources/appnoteabstract.jhtml?abstractName=sboa092a





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