Low noise opamps without input diodes?

Mar 20, 2007 30 Replies

....

nop soz not without looking again, seem to remember the old ne5534... stil being there and making sure there are no hidden input diodes is a bit of a pain sometimes.

There are some improved lm358 types but these tend to have diodes. Ive got a couple of such types of op amps wich were usless for what I needed at the time becuase of input diodes but would otherwise do quite well for what you need.

Colin =^.^=

That one does have the diodes :-(

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Diodes unfortunately disqualify the parts except for clean amplifier apps. But there I can easily design a low noise amp with discretes anyway.

Regards, Joerg http://www.analogconsultants.com

this one ...

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?

Colin =^.^=

That one would be good as well. Has diodes but these are zeners and one can usually live with the 10V differential they allow. However, the price is many times higher than for example the LM833.

Regards, Joerg http://www.analogconsultants.com

"Joerg"

** You after DIL or SMD pack ?

The one above is SMD only.

........ Phil

Maxim makes a *comparator* with back-to-back input diodes. Talk about unclear on the concept!

John

You might want to verify that the offset voltage won't be altered as you put extreme differential voltage on the inputs. Generally, that is why you put the protection diodes on the dif pair.

I assume you will check for phase reversal.

It won't be more than 3-4V.

Regards, Joerg http://www.analogconsultants.com

Actually SMD is perfect. Digikey also has them in DIP (from ST) if you ever need that. The DIP version is Digikey P/N 497-1598-5-ND and it's currently in stock. There is also a DIP version from National but Digikey is out of stock on that one.

I was thinking of getting a few DIPs as well because I we did the prototype in thru-hole. However, that'll be an ugly hack because it was done with quad opamps in sockets. It'll look like little Eiffel towers ;-)

Regards, Joerg http://www.analogconsultants.com

ROFL! Luckily I have already had my morning coffee, else I'd be wiping off the monitor now.

Regards, Joerg http://www.analogconsultants.com

You are NOISE .

There is nothing new in analogue Op Amps and there never will be .

The fast lane is to simply search existing , leading applications , and then merely buy what they used or compromise a bit to hit your target .

First you must duplicate that app'

Then mod circuit for your objective ----------------

Some ppl use a known fault in an I.C. to throw you off course . CD4___ . T.I. , long ago made CD4007 ? . If you held both CLK and RESET pins together , it did not act proper. Burr Brown Res' used this in an oscillator "722" and got burned ( Sole sourced = bad)

Thus , in your characterization of their application of that I.C. , you must consider this and purposely "push" the envelope , to learn if their are any anomolies , not mentioned in SPECs .

I do E.E. . I make profits .

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