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Old 12th December 2006, 12:00 PM   #1
lineup is offline lineup  Sweden
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Lightbulb AD797 Clone people! Who can make a better one.

hi

Everything tells me, that AD797 is not only a very good operational amplifier
The topology used has got to be something extremely good!

Using only the simplified schematic from Analog Devices datasheet
I get some extraordinary simulation results.
(And I am used to see a few good figures, from my own circuits. Using same transistors.)

===============================

A few details from me, for those who want to try to make a better AD797 Clone.
... but I am not sure anyone could do this better than myself
... maybe get some similar results, but not better, I doubt.

My circuit is in attachment and follows the AD797 schematic
- what I know from reading This Datasheet Very Closely

Quote:
Lineup Audio Lab
AD797 Clone - version 2a
by lineup

... Supply +/- 15 Volt DC
... Test 10 Volt RMS into 2.2 kohm, = 14.14 Volt peak!!!
... Gain= x10, +20dB
... Frequency, -3dB at 600kHz
... THD <0.001%, my MultiSim does not show anything = 0.000%, see picture

Some more details:
All transistors BC550C and BC560C.
Total Supply Current 8.0 mA
Output stage, like the original biased only 0.5 mA ( 492uA more precise .... )
Good Luck Fellowes!
You may need really it

Regards
lineup
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File Type: png ad797clone-2a_10vrms.png (20.8 KB, 4094 views)
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Old 12th December 2006, 12:09 PM   #2
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Hi, Lineup,

How about LM4562 ? Do you know what is the simplified schematic of this opamp?
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Old 12th December 2006, 12:38 PM   #3
PMA is offline PMA  Europe
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Why did you cover the folded cascodes and current sources, connected to input differential pair?
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Old 12th December 2006, 12:58 PM   #4
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Default Re: AD797 Clone people! Who can make a better one.

Quote:
Originally posted by lineup
hi

Everything tells me, that AD797 is not only a very good operational amplifier
The topology used has got to be something extremely good!

Using only the simplified schematic from Analog Devices datasheet
I get some extraordinary simulation results.
(And I am used to see a few good figures, from my own circuits. Using same transistors.)

===============================

A few details from me, for those who want to try to make a better AD797 Clone.
... but I am not sure anyone could do this better than myself
... maybe get some similar results, but not better, I doubt.

My circuit is in attachment and follows the AD797 schematic
- what I know from reading This Datasheet Very Closely



Good Luck Fellowes!
You may need really it

Regards
lineup

In the sim you have perfectly matched current sources, perfectly matched transistors, of course your THD is close to zero.

Jan Didden
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Old 12th December 2006, 04:08 PM   #5
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Linup,

did you use the compensation cap(s) to reduce distorsion, as suggested in the datasheet?
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Old 21st December 2006, 09:39 AM   #6
lineup is offline lineup  Sweden
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Thumbs up Re: AD797 Clone people!

Quote:
Originally posted by lineup

Using only the simplified schematic from Analog Devices datasheet
I get some extraordinary simulation results.

A few details from me, for those who want to try to make a better AD797 Clone.
... but I am not sure anyone could do this better than myself
... maybe get some similar results, but not better, I doubt.

My circuit is in attachment and follows the AD797 schematic
.


The above was an AD797 Analog Devices operational amplifier CLONE.
Where I tried to make as perfect discrete copy as possible
of this high very performance and expensive AD797


I now have used same basic topology, with some changes
to try to get some other 'improved features and data'.
The circuit still has got a diamond output buffer,
but here I have used Low Noise High Voltage JFET 2SK373, 100V, for input pair.
Instead of low-noise bipolar BC550C, 45V
And 150V transistors 2N5551 - 2N5401 for rest of this amplifier.
This gives my New Op-Amp Max supply of 100 VDC, or Dual supply +/-50 Volt.

Test results at unity gain and +/- 40 VDC
were performed at 1kHz
- 20 VRMS input = output. Peak: 28.9 volt input ... 28.3 volt out
- Into 2 kOhm resistor LOAD
THD shows 0.000%
See link below for Fourier analys of Separate Harmonics.

================================================


My simulation test setup of this discrete Op-Amp here:
http://www.diyaudio.com/forums/attac...amp=1166531312 (image)

Read more details of this Lineup Audio Project
and about 2SK373 JFET for 100 Volt

in this post:
Extreme Performance Discrete Op Amp - 2SK373 2N5551 2N5401



Regards
lineup discrete op amp man
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Old 21st December 2006, 11:32 AM   #7
thanh is offline thanh  Viet Nam
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Your job is very intersted in. Can I view the schematic with all detail ?
thanks!
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Old 21st December 2006, 12:34 PM   #8
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As janneman hinted earlier, anyone can build a 'perfect' circuit in a simulator. There is a great deal of difference between the fantasy of perfect components and the reality of imperfect parts out in the real world. Even matched transistors do not approach the ideal units in a simulator.

Grey
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Old 21st December 2006, 12:45 PM   #9
edl is offline edl  Hungary
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Halojoy (Lineup),

This topic is a joke (too).


GRollins,

I agree!


Regards,
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Old 21st December 2006, 01:03 PM   #10
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Lineup......What software are you using for analysis ?
Thanks.
Ashok.
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