TI opamp

I know audiophiles wet their panties over that one...if you do a Google search on it a lot of designs from audio enthusiast sites pop up

I'd like to get it into my LT Spice circuit, but TI only furnishes Pspice and Tina models, so I'll have to shoehorn one of them into LT Spice. The models are huge.

As a shortcut, I could use the UniversalOpamp model and plug in the key specs, but I can't find documentation on that, either. Like, what does the noise parameter 'en' actually do? Or 'enk' ?

On a sunny day (Mon, 09 Mar 2015 20:36:05 -0700) it happened John Larkin wrote in :

Depends who is listening I suppose. A good audiophile can easily hear 0.000001%.

Well the LME suggests that they got it when they took over National Semiconductor, so it might be okay.

TI has been known to publish data sheets on the basis that if they get enough interest they'll try to make the part that matches the data sheet.

/Real/ audiophiles don't use opamps !

/Real/ audiophiles are notorious lunatics. I have a long list somewhere around of idiotic audio terms, like "macrodynamics" and "soundstaging" and "bass speed."

This amp looks better than the LT1028. I hope it doesn't have a similar noise peak off the graph.

Yup. The ADI low-noise amps, still relatively noisy, are slow. The LT1028 is below 1 nv/rthz but has issues.

Sure looks it.

Nice opamp..Thanks, well lotsa current noise, and the slew rate is a bit slow for a 100MHz GBW. Too bad they don't show the noise plots out past 100kHz. (Maybe someone will measure it?)

George H.

The AD797 is another - better - alternative to the LT1028. I suggested it b ack in about 1997 when somebody was looking for an alternative to the LT102

Some audiophiles used integrated circuits for more or less rational reasons . They aren't all lunatics. People like Peter Baxandall and Peter Walker qu alified as audiophiles, but despised the subjectivists quite as much as you do - and probably for better reasons.

Probably BiCMOS. Look at the input bias current... bipolar input stage... could possibly be all bipolar given the 38V total supply capability. ...Jim Thompson

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I've looked at that part in the past, but never used it. It's quiet, like the ADA4898, runs off +-15V, has excellent linearity, and its PSR and CMR are amazing.

Its main drawback is a crappy slew rate: 22 V/us for a 110 MHz GBW.

Cheers

Phil Hobbs

The ADA4898 is about 90 MHz, and the ADA4899 is 500 MHz GBW, though limited to +-5V.

Cheers

Phil Hobbs

But 22V/us is plenty good enough for audio... that's a "power" bandwidth of ~300kHz. ...Jim Thompson

Sure thing. But clearly they traded off speed for other things. The classical 741-style architecture with no current boosters or emitter degeneration gets you a slew rate of about 0.3V*GBW, and this one is only 70% of even that. I guess they did that to get more phase margin, perhaps?

Cheers

Phil Hobbs

True. But it's cheap!

Sure, the front end is likely giant NPNs with lots of current, to keep the voltage noise down. It probably has bias current cancellation, which makes the current noise worse, if anything. OP-27 sort of thing.

Probably all bipolar.

Am 10.03.2015 um 15:57 schrieb John Larkin:

The AD797 is not significantly noisier or slower, if at all. I really like the ADA4898-2.

Depending on how it's measured, a little bit lower ft than the LME, but more than twice the slew rate, no 300 KHz noise mole hill like LT1028, and with 2 amplifiers/SO-8 quite a good price, especially if you average

and, related:

regards, Gerhard

Probably phase margin. Slew rate, GBW, and phase margin are all interrelated with input stage current and the pole-splitting capacitor.

See Op-Amp-Config.zip on the Device Models & Subcircuits Page of my website. Simply plugging into the subcircuit the parameters for slew rate, GBW and phase margin, from a datasheet, will get you quite close to actual performance.

(I need to update that model to include swing limits, current limiting and rail currents... I know how, having done it making a model for a commercial customer... just haven't gotten round tuit ;-) ...Jim Thompson

Yes they do. They use _tube_ op amps.