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Old 15th January 2014, 09:07 AM   #1221
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What about this?
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File Type: asc Circlophone-MOS-CCS-BUF.asc (10.6 KB, 39 views)
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Old 15th January 2014, 10:11 AM   #1222
Elvee is online now Elvee  Belgium
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It was stable, but the phase margin was a bit short, in the region of 44°.

I have made some changes, and now it is well over 100°:
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Old 15th January 2014, 10:40 AM   #1223
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Quote:
Originally Posted by Elvee View Post
It was stable, but the phase margin was a bit short, in the region of 44°.

I have made some changes, and now it is well over 100°:
Thank you Elvee. Square wave has excessive overshoot issue with this one but I'm not sure that is it a bad indicator or not. I just added some pF parallel to fb resistor but it didn't help.

EDIT: Very low main compensation cap (C4) like ~10pF fixes it, but phase margin is in question again. Reducing R24 also helps.

Last edited by terranigma; 15th January 2014 at 11:05 AM.
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Old 23rd February 2014, 05:36 PM   #1224
tvrgeek is offline tvrgeek  United States
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Taking a look here for my education. The first thing I see is you manage not to turn off the outputs. Big first step!
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Old 13th December 2014, 09:36 PM   #1225
hahfran is offline hahfran  Germany
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Hi
having not much time to read thru the thread, I think anyway this amp cannot be redesigned for complimentary output stage and should not use high ft power BJTs without more redesign. Is that correct?
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Old 14th December 2014, 08:53 AM   #1226
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Quote:
Originally Posted by hahfran View Post
Hi
having not much time to read thru the thread, I think anyway this amp cannot be redesigned for complimentary output stage and should not use high ft power BJTs without more redesign. Is that correct?
Have a look at this thread:

Building Elvee's Circlophone: Documentation, Parts, Accessories, & beginner friendly
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Old 14th December 2014, 09:07 AM   #1227
Elvee is online now Elvee  Belgium
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Quote:
Originally Posted by hahfran View Post
Hi
having not much time to read thru the thread, I think anyway this amp cannot be redesigned for complimentary output stage
Correct
Quote:
and should not use high ft power BJTs without more redesign. Is that correct?
Not quite: I have tested transistors having >30MHz Ft, and other members have gone further.
With attention to the layout and adaptation of the local compensations, it poses no particular problem
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Old 14th December 2014, 10:12 AM   #1228
hahfran is offline hahfran  Germany
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Thanks. I refer to the fT vs ic The original process 2N3055 was single diffused for these devices the fT vs ic is almost flat. But not so for triple diffused, multi-emitter etc. At ic about 50 mA fT is as low as 200 kHz, for ic = 2-4 A ft is 60 Mhz, for ic = 7 A and up fT is back to 100 kHz.
As i have some matched Sanken complimentary pairs...not nice that the circuit cannot be redesigned for complimentary OS
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Old 14th December 2014, 12:45 PM   #1229
Elvee is online now Elvee  Belgium
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Quote:
Originally Posted by hahfran View Post
.not nice that the circuit cannot be redesigned for complimentary OS
Well, the basic idea was precisely to avoid complementary pairs, because of the unavoidably imperfect matching inherent to the differences in N and P devices made from silicon.
Same sex transistors can be perfectly symetrical.

Note that the principles, if not the architecture can be ported to complementary topologies. Serach for "symclophone" and "synclophone". These haven't been prototyped, but there is no reason they wouldn't work in practice.
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Old 14th December 2014, 05:50 PM   #1230
hahfran is offline hahfran  Germany
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Yes the thing with electrons and holes...the ratio of carrier mobility is 2, and that factor shows up everywhere, for ex. in the values of Cgs of MOSfets. Perfect complimentary pairs are not possible, but almost, and here BJTs excel over Mosfets. There is however no free lunch some price is to be paid in terms of level shifting, here with zeners, which are here avalanche diodes adding random noise ( at best ) and temperature coefficients. Anyway it is as symmetric as symmetric can go. Very clever topology the circlophone.
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