AD797 Clone people! Who can make a better one.

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#62
Hi Andrew,

At the moment I don't have any...I have given away for free all I have. But I could easily produce any quantity you or anyone else needs. The problem is that I don't have a remote idea how to organise payment and other bits and pieces.

And I don't have a dig. camera to take a image of the reverse side, sorry...I just use a friend with it to take a image for occasion.
 
#69
aparatusonitus said:


Not in my text book...in fact I see it as a very simple, elegant and extremely well behaved circuit... two tumbs up for Scott Wurcer.

If I could lend my hands to Philips BC846(B)S, BC857(B)S, BC850, 860 as well as BCP54/55/56 and BCP51/52/53 I'd start to buid it immediately. With these transistors, I think it will not be expensive to build at all, if you can deal with SMD parts.
Click to expand...

Just found that Buerklin stock this transistors and a little shop in my hometown as a distributor, so I'll start to creating new devices in Eagle, 'cos there is none dual transistors in SOT363 package...what a pain:bawling:
 
#70
I don't believe any discrete version of AD797 can close to the performance of integrated AD797. For one simple thing, can you make your discrete opamp with 0.1mV Vos over the common-mode range?

Yes, you can make -3dB frequency at 600kHz with ideal current source. If you put any real transistor on it, you amp will oscillate. Think about what is your Avo!?

I have measured some of AD797 with AP2700. And I found that the distortion of AD797 is virtually null. All THD+N number come from the thermal noise of the opamp.
 
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#71
kwkam said:
I don't believe any discrete version of AD797 can close to the performance of integrated AD797. For one simple thing, can you make your discrete opamp with 0.1mV Vos over the common-mode range?

Yes, you can make -3dB frequency at 600kHz with ideal current source. If you put any real transistor on it, you amp will oscillate. Think about what is your Avo!?

I have measured some of AD797 with AP2700. And I found that the distortion of AD797 is virtually null. All THD+N number come from the thermal noise of the opamp.
Click to expand...

With LM394 at input or equivalent, I believe this low offset is possible.

Best comparing to discrete using 600R load, >5kHz, 10V (pk) OP swing and some real gain of say 30.

You will see distortion then.

cheers

Terry
 
#72
In the case of using LM394. I don't know is it still discrete opamp. Instead of Vbe mis-match in differential pair. Discrete opamp is hard to make systematic offset as low as 0.1mV

And that is reason why people make 741 years ago.
 
#73
AD797: what a nice scheme!

Hello,

I was attracted by the elegance of the AD797 schematic (well, the simplified schematic only is available) and so I decided to reproduce it on LTSpice.
Here my interpretation, maybe one day I will make it as discrete one:
any opinion?
 

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#74
gugol said:
Hello,

I was attracted by the elegance of the AD797 schematic (well, the simplified schematic only is available) and so I decided to reproduce it on LTSpice.
Here my interpretation, maybe one day I will make it as discrete one:
any opinion?
Click to expand...

Differential input stage -> folded-cascode VAS with shunt compensation -> diamond buffer output stage.

The novelty is the current mirror of the VAS is bootstrapped. It should benefit its open-loop bandwidth.

As the vas stage has no current gain, it may lack gain as standalone power amp. For an audio amplifier, you want at least 23dB gain after closing the loop. Plus 50dB negative feedback at 1KHz.
 
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#75
aparatusonitus said:
AD797 Clone people! Who can make a better one?

I think I manage to bit you lineup😀 ...at least my sim tells me so
:cannotbe:

Below you'll find a circuit and FFt diagram at 1kHz and 20kHz (output at 1Vpp, load 600R)
ad797 v.1.3_page-0001~3.jpg
Click to expand...
Made this , Circuit working, it has only one problem, whenever I remove input signal,getting dc9v plus out and when connecting signal from phone jack it's become 1.8mv offset and works, why without signal or any input connection getting DC out and circuit not working 🤔 any fix?
 
#79
But u can publish for diy users or for personal users, it's pretty old clone tried to make it cause it's simulated but not made by any other, but now 2024 if anyone modified it for better performance, then that's will much better damn sure 👍
 
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