opamps used for unity gain - Page 2

PMA · 26th November 2007, 06:58 PM

627 is fine at unity gain.

juma · 26th November 2007, 07:27 PM

AD797 - properly implemented, it's the best sounding opamp in unity gain configuration (chosen among 20-30 most popular and best specified opamps made by TI, Analog, Linear).

It even sounds better than many discrete buffers.

Don't worry too much about NFB. It's not good or bad by itself , it will just reveal topology behind it.

http://www.diyaudio.com/forums/showt...927#post980927

PMA · 26th November 2007, 07:45 PM

The AD797 is UNSTABLE at unity gain.

Conrad Hoffman · 26th November 2007, 07:52 PM

Of course, you can build a unity gain stable circuit with *any* opamp, regardless of its internal compensation. If I'm limited to two resistors and two bypass caps, then my options are a bit more limited ;-)

PMA · 26th November 2007, 07:59 PM

You can make it "stable", but it is not the best way how to use the AD797.

Conrad Hoffman · 26th November 2007, 09:44 PM

True enough, and it might not be my first choice for a unity gain buffer, though it can be forced to do the job. IMO, the 797 has a great data sheet, and op amp "rollers" would be wise to read it carefully. It ain't necessarily plug & play with a lot of other parts, unless you mod the circuit accordingly, which sort of makes my original point.

juma · 26th November 2007, 10:57 PM

Quote:

Originally posted by PMA
The AD797 is UNSTABLE at unity gain.
You can make it "stable", but it is not the best way how to use the AD797.

Sorry PMA, but according to my extensive experience with this chip - what you are saying is simply not true.

AD797 is absolutely stable at unity gain - I've built numerous circuits with it and there was no sign of instability at all.

I don't wish any further argument on this subject - I'm talking out of experience, not waving with the paper.

SY · 26th November 2007, 11:09 PM

Oh, Scott... Scott... Can you hear me?

juma · 26th November 2007, 11:25 PM

Yes, Scott Wurcer is the man who designed AD797 and he is the member of diyaudio.
He might say a word or two about it

HiFiNutNut · 26th November 2007, 11:47 PM

Thanks, guys. Please keep your input coming and let us newbies be educated.

Yes, to me the comments I read from the other forum were more of a myth. I have used opa2134 mainly, most in unity gain and have not subjectively found any audible problem. I'd say the system is pretty much of high fidelity, although I must confess that opa627 was subjectively better in one of my experiments.

So, is AD797 the best for unity gain? Juma, would you mind sharing on how to properly implement it?

26th November 2007, 11:09 PM	#18
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Oh, Scott... Scott... Can you hear me? __________________ "...we stumble and get up, we are sad, confident, insecure, feel loneliness and joy and love. There is nothing more; but I want nothing more.” - Christopher Hitchens 1949-2011

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26th November 2007, 06:58 PM	#11
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	627 is fine at unity gain.

26th November 2007, 07:27 PM	#12
juma diyAudio Member Join Date: Nov 2005 Location: Zemun	AD797 - properly implemented, it's the best sounding opamp in unity gain configuration (chosen among 20-30 most popular and best specified opamps made by TI, Analog, Linear). It even sounds better than many discrete buffers. Don't worry too much about NFB. It's not good or bad by itself , it will just reveal topology behind it. http://www.diyaudio.com/forums/showt...927#post980927

26th November 2007, 07:45 PM	#13
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	The AD797 is UNSTABLE at unity gain.

26th November 2007, 07:52 PM	#14
Conrad Hoffman diyAudio Member Join Date: Mar 2007 Location: Canandaigua, NY USA	Of course, you can build a unity gain stable circuit with any opamp, regardless of its internal compensation. If I'm limited to two resistors and two bypass caps, then my options are a bit more limited ;-)

26th November 2007, 09:44 PM	#16
Conrad Hoffman diyAudio Member Join Date: Mar 2007 Location: Canandaigua, NY USA	True enough, and it might not be my first choice for a unity gain buffer, though it can be forced to do the job. IMO, the 797 has a great data sheet, and op amp "rollers" would be wise to read it carefully. It ain't necessarily plug & play with a lot of other parts, unless you mod the circuit accordingly, which sort of makes my original point.

26th November 2007, 11:25 PM	#19
juma diyAudio Member Join Date: Nov 2005 Location: Zemun	Yes, Scott Wurcer is the man who designed AD797 and he is the member of diyaudio. He might say a word or two about it

26th November 2007, 11:47 PM	#20
HiFiNutNut diyAudio Member Join Date: May 2004 Location: Sydney	Thanks, guys. Please keep your input coming and let us newbies be educated. Yes, to me the comments I read from the other forum were more of a myth. I have used opa2134 mainly, most in unity gain and have not subjectively found any audible problem. I'd say the system is pretty much of high fidelity, although I must confess that opa627 was subjectively better in one of my experiments. So, is AD797 the best for unity gain? Juma, would you mind sharing on how to properly implement it?

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