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Old 3rd October 2013, 08:10 AM   #21
wahab is offline wahab  Algeria
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Quote:
Originally Posted by Bonsai View Post
Good distortion results and slew rate on your design dadod.
The original design is from Manso IIRC , yet there s no indication
of this in the opening post.....
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Old 3rd October 2013, 08:23 AM   #22
dadod is online now dadod  Croatia
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Quote:
Originally Posted by wahab View Post
The original design is from Manso IIRC , yet there s no indication
of this in the opening post.....
If you read CFA thread you can see there that manso design is the one I came back after some circles CFA Topology Audio Amplifiers. It is a bit different specially type of compensation. This one is just more powerful version of the mosfet version I presented there.

Last edited by dadod; 3rd October 2013 at 08:31 AM.
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Old 3rd October 2013, 09:01 AM   #23
mcd99uk is offline mcd99uk  United Kingdom
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This design topology is a natural end point in CFA design.

I ended up with a similar design independent of Manso's design.

Edit: Wonder if the TPC compensation can be simplified (as it is symmetrical) a little to reduce component count and reduce compensation based VAS fighting.
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Old 3rd October 2013, 09:31 AM   #24
dadod is online now dadod  Croatia
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Quote:
Originally Posted by mcd99uk View Post
This design topology is a natural end point in CFA design.

I ended up with a similar design independent of Manso's design.

Edit: Wonder if the TPC compensation can be simplified (as it is symmetrical) a little to reduce component count and reduce compensation based VAS fighting.
Actually it's possible, I did it in the VSSA thread before.
Here is simpler TPC.
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Old 3rd October 2013, 09:46 AM   #25
mcd99uk is offline mcd99uk  United Kingdom
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Originally Posted by dadod View Post
Actually it's possible, I did it in the VSSA thread before.
Here is simpler TPC.
This is exactly what I had in mind.
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Old 4th October 2013, 10:20 AM   #26
dadod is online now dadod  Croatia
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Here is low power versions of LMOS CFA amp with simplified TPC, one with lower loop gain(LG 78 db up to 10kHz) and one with higher LG(120 dB up to 1kHz).
High power AMP should give even better result.
It is interesting to see IMD for those two different LG.
Input signals 19kHz and 20kHz amplitude 1.2Vpp.
IMD for lower LG is 116 dB and for higher LG it is 157 dB
Does more complication is worth much lower IMD??
Damir
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File Type: jpg CFA-100W-lowLG-sch.jpg (102.6 KB, 518 views)
File Type: jpg CFA-100W-lowLG-CCIF-IM.jpg (204.9 KB, 481 views)
File Type: jpg CFA-100W-highLG-sch.jpg (108.4 KB, 463 views)
File Type: jpg CFA-100W-highLG-CCIF-IM.jpg (202.7 KB, 441 views)
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Old 4th October 2013, 10:44 AM   #27
mcd99uk is offline mcd99uk  United Kingdom
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I see this idea has resurfaced and you've found a better compensation method.

It's interesting to note the IMD differences. You should reference this in the CFA thread.

Have you found a way of extending the LG up further than 1KHz in the more complex version. Its not easy, I've found.
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Old 4th October 2013, 11:12 AM   #28
dadod is online now dadod  Croatia
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Quote:
Originally Posted by mcd99uk View Post
I see this idea has resurfaced and you've found a better compensation method.

It's interesting to note the IMD differences. You should reference this in the CFA thread.

Have you found a way of extending the LG up further than 1KHz in the more complex version. Its not easy, I've found.
No I did not, I think that there is the pole at the same frequency, just shunted in low LG amp.
I don't think that it's important as IMD is normaly manifestad at lower frequences, imput filter should prevent to high frequiences input the amp(maybe better input filter as Edmond suggested before).
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Old 4th October 2013, 12:39 PM   #29
mcd99uk is offline mcd99uk  United Kingdom
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It would be good to get the loop gain flat out to 5KHz so we could achieve flat THD performance up to this frequency.

Loop gain of 120dB is up there with the VFAs.
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Old 4th October 2013, 12:42 PM   #30
dadod is online now dadod  Croatia
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Quote:
Originally Posted by mcd99uk View Post
It would be good to get the loop gain flat out to 5KHz so we could achieve flat THD performance up to this frequency.

Loop gain of 120dB is up there with the VFAs.
Yes, but don't forget distortion at 1 kHz .000001%, I never seen that in VFA amp simulation.
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