Low noise opamps without input diodes?

Yes, there are some... shit, I remember you were boycotting National and Phillips because of their fancy websites, they are cheaper, but what to do! Maxim and LT also -cazzo, there they go then maybe AD? ADA4004, OP467 Otherwise just thow together some discretes, because those mentioned are above 80c.

JFET amplifiers may be your best choice. LTC's LT1792 has only 4.2nV/rt-Hz typical and allows a wide differential swing, AFAICT. You didn't mention bandwidth requirements. BTW, you can make a composite two-opamp opamp to get the bandwidth you might need, and the input performance you need. OTOH, if you want superior performance and rock-bottom prices, remember, somebody has to pay the bills for the development of today's high-performance ICs.

"Joerg"

Bout 40 cents each.

....... Phil

That leaves out a lot of choices, next best thing to OPA from TI at least seems to be TLC070 etc I was going to suggest TLV274 wich I just used but looked up vn is 39nv the other chip I use is opa2354, I too needed to use them as comparators so no input diodes.

Colin =^.^=

Thanks, Win. It's a great amp. Unfortunately it seems to come only in singles and then the roughly $2.50 a pop begin to hurt. Ban suggested the OP467 which is a bit higher with its 6nv/rtHz but still not bad at all.

Bandwidth is low, a few kHz and mostly used as integrators, limiters etc.

This one doesn't have to be rock-bottom in cost, just reasonable. Of course I was quietly hoping there would be a supercharged TL084 somewhere for just a few pennies more :-)

Whoa! Now that's a great amp. Hadn't heard of it before. What makes me cringe though is that +/-15V supplies are now marketed as some kind of specialty "high voltage" feature. It used to be standard for all analog stuff (and as far as I'm concerned it still is).

robert

Joerg, together with the noise you have to specify the bandwidth. Most very low noise opamps have extensive bandwidths, actually all opamps I remember with GBWs from a few 100MHz are specified as very low noise with figures in the range of 3nV/rtHz and below

Rene

That makes me cringe as well. For lots of dynamic range it's hard to live with 5V or so. What good does a really low-noise performance do when the top of the dynamic range is chopped off?

Neat! Thanks. Comes only in duals but heck, can't beat that price. And it is 2nd sourced, found it also at ST and ON-Semi. This one ought to be really popular with high end audio guys yet for some reason I have never heard them talk about it.

It's below audio in this case. High GBW would not be a problem but the few that are in the +/-15V range such as some THS devices cannot tolerate much differential input.

I am going to check out Phil's suggestion, the LM833. Best of all, that one is multi-sourced.

It's just too cheap.

robert

Plus those high GBW opamps generally are low noise at high frequency and have a pretty high 1/F corner frequency. Even bipolar opamps.

Mosfet and

Bipolar .

Bipolar has almost no change in input current. Thus the voltage drop across the input R's\ is no problem . Accurate .

MOSFETs have a extreme TEMPCO , thus their input Z is meaningless . It may as well be 50K ohm , to swamp out the extreme input current changes . They are 4 times higher B.W. .

Noise is very low in Bipolar OpAmps . But low noise is also very low B.W.

Have you noticed the old Bipolar Op Amps are still very useful ? MOSFETs did not obsolete Bipolars ..

Ah, that's the solution: Gold-plate its pins and top it off with a glass dome that shows the part number in pseudo-3D. Maybe with a blue LED in there.

Werty a écrit :

I can see you have very deep understanding of the subject. Sort of.

On Wed, 21 Mar 2007 22:09:33 +0100, in sci.electronics.design Fred Bartoli

ROFL, thanks Fred

martin

Yes I think I remember looking at that one once, but you talk of high-Z nodes, wont the bias current be a problem ?

If its not then there are a few more with not so low bias current on the TI list.

Colin =^.^=

Well, it doesn't exactly help, of course, but I may be able to live with If its not then there are a few more with not so low bias current on the TI

I'll have to go through it again. Any particular ones that come to mind? I rarely use low noise opamps since I design most of my stuff in discretes. Mainly to maintain true 2nd-sourcing for everything. Opamps are mostly relegated to more mundane jobs in my designs.