op-amps with wide open-loop bandwidth ?

Opamps are rated for speed in units of gain times bandwidth, or gain bandwidth product. What open loop gain are you looking for at 20 kHz?

: > Thanks. : > Dave Moore : >

: >

: Opamps are rated for speed in units of gain times bandwidth, or gain : bandwidth product. What open loop gain are you looking for at 20 kHz?

Unity or above.

Above = better :-)

KHz? It would be very hard to find one that slow.

John

"Dave Moore"

** Huh ??

Do you even know what "open loop bandwidth " is ??

The "unity" gain frequency of common "audio" op-amps varies from 1MHz to 10 MHz.

....... Phil

Oops, "unity" isn't what I meant. I mean, I want any op-amp that is flat (more or less) to 20Khz I'm not looking for any specific specs beyond that, so it's V/mv gain curve isn't so important as long as long as it's reasonable to 20KHz also

I'm simply looking for a wide variety of op-amp types for sonic evaluation. IOW, I'm attempting to correlate what my ear hears with with the variations in specs from one op-amp to another and sadly deficient in the list of op-amps I've evaluated so far are any that are flat open-loop to 20Khz or higher. The best I have on hand are 10KHz.

So far my short list of star performers via the old golden ear test are; THS4022, THS4052, THS4062, THS4012, AD828, LT1363

Although it should be mentioned that these are for guitar amplifiers and that Audio Hi-Fi enthusiasts might not agree about the merits of the afore mentioned.

DM

: : > Thanks. : : > Dave Moore : : >

: : >

: : Opamps are rated for speed in units of gain times bandwidth, or gain : : bandwidth product. What open loop gain are you looking for at 20 kHz? : : : Unity or above. : : Above = better :-) : :

sorry, multiplexing error on my part. I addressed that in a different post.

: > : > Anyone know of any op-amps with : > : > open-loop bandwidth in excess of 20KHz ? : > : >

: > : > Thanks. : > : > Dave Moore : > : >

: > : >

: > : Opamps are rated for speed in units of gain times bandwidth, or gain : > : bandwidth product. What open loop gain are you looking for at 20 kHz? : >

: >

: > Unity or above. : >

: > Above = better :-) : : : : ** Huh ?? : : Do you even know what "open loop bandwidth " is ?? : : The "unity" gain frequency of common "audio" op-amps varies from 1MHz to 10 : MHz. : : : : ....... Phil : :

: >Thanks. : >Dave Moore : >

: : KHz? It would be very hard to find one that slow. : : John

Sorry, Let me try again. I want one with an open-loop gain that's relatively flat and doesn't start to roll off until 20KHz or higher. :

"Dave Moore

** What exactly is it you wanted ?

Was it open loop or fruit loop ??

......... Phil

Yeah, most start to roll off in the 10-100 Hz range.

AD825 comes close (about 15kHz with a +/-15V supply).

See fig. 12:

Best regards, Spehro Pefhany

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Since the OpAmps were designed for closed loops, it appears to be an almost infinitely bad idea to use them open loop. What do you want to achieve ?

Rene

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Hi Dave,

Nobody will use an opamp with open loop. So what you may need is a very high oen loop gain for great linearity in close loop configuration and this with very high gain bandwith and very low noise. But anyway, make pure gold around and place a few old tubes around and every hifli enthusiast will praise you...

regards

Marte

The whole idea of opamps is that, if they have enough extra gain to throw away, at the frequencies you are interested in, then they all act the same. But the definition of "enough extra gain" is highly dependent on the circuit they are part of. In other words, if the opamp is fast enough and has high enough gain, it disappears as a source of sound color, and the other, more predictable components in the circuit, program its output, almost completely. The effect of gain on, say, a unity gain follower is very different than the effect of gain on a distortion effect generator, at the same frequency. So, before any suggestion is likely to help you, we need to understand a lot more about what circuit you intend to use this opamp in.

And since, it is fairly obvious that you are not yet a circuit designer, you would probably get a more helpful response if you start over in sci.electronics.basics

Good luck.

"John Popelish" <

** That's telling him - John !!

The little sook will cry himslef to sleep over that one .....

......... Phil ;-)

There's no way you can run audio through an op-amp, open-loop.

Open-loop is going to give you a voltage gain of 50,000 to a million or more, and very high distortion too. That's because op-amps are designed to be run with a lot of negative feedback. Always. Unless you're using one as a comparator, which is a mediocre idea usually, and you're not doing this anyway.

Negative feedback is so common, most spec sheets don't even show the input/output transfer function-- it's enough to know it's crummy and unusable as an amplifier.

"Ancient_Hacker"

** There is no way the OP wants to do that. ** The OP is of the view - first brought to international notoriety by Matti Otala in 1980 IIRC - that an audio amplifier needs to have an open loop bandwidth that includes the audio band

It was bunkum.

Many have since proved it was bunkum.

Matti was a troll.

....... Phil

As are most usenet self-styled experts...The OP is a good example of the web educated product, totally confused. If the idiot has been dabbling his life away with audio electronics piddling for the past 10 years and yet cannot find the stamina to read through a simple text like Mancini's OP Amps for Everyone, and Mancini means *everyone* regardless of intellectual abilities, then let him go rot.

Dave,

Check out the ComLinear CLC 425.

Nobody seems to be taking your question at face value. Can't say I blame them, but there are lots of op amps that meet that simple requirement.

For example:

--AD8099

--OPA847 (and others in the OPA84x family)

--OPA695

--ZL40123

--LMH6738 etc, etc.

(Some [most?] will make dandy oscillators for you too, if you try to use your normal audio construction techniques...)

Cheers, Tom

In article , Dave Moore wrote: [...]

The open-loop bandwidth of the op-amp doesn't matter as others have told you but, if you really want to give it a try, some op-amps ( I think the LM308 is one) can be made to have a bandwidth like this by connecting a resistor from the compensation pin (8 IIRC) to system ground.

Other op-amps will be destroyed so be careful to check. I will predict for you what the LM308 would sound like when you do this just to save you some time.

It will sound "chew your own leg off" bad!

I hope this helps.

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