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Old 25th November 2011, 11:25 PM   #331
Piersma is offline Piersma  Netherlands
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Default Corrected schematic

the complementary Elvee circlophone.
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Old 26th November 2011, 03:24 PM   #332
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by Piersma View Post
the complementary Elvee circlophone.
Waow! this circlophone is not "little and cheap" anymore: it is the "Posh Circlophone".


There are many worthwhile improvements possible over the basic topology.

The posh version includes one of the most useful: a FET input, that eliminates trade-offs between bias current modulation and input impedance.

The other modifications are quite sensible too.

I see one other point where easy improvements can be gained: replace R27 by a 2-wire current source (I have described some suitable varieties in other topics).
This will improve the PSRR, make R22 superfluous, and allow the same circuit to work from +/-10 to +/-100V without alteration.

Excellent work.
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Old 29th November 2011, 09:00 AM   #333
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Hello Elvee,

I wonder that how this topology sensitive for faster output transistors (10~80 mhz). You pointed already that C12 should be 820pF for faster devices. Have you any suggesting indicator for sure that amplifier is healthy or not?

And bridged configuration.. has topology any drawback regarding to two amplifiers as bridged configuration? In this case, can we avoid source signal ground connected to each amplifier regarding to use of balanced signal?

Last edited by terranigma; 29th November 2011 at 09:23 AM.
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Old 29th November 2011, 07:19 PM   #334
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Quote:
Originally Posted by powerflux View Post
printed PDF's, filled in the componentvalues. i really hope i didn't make mistakes. thank you for your patience
Hello powerflux,

I etched and drilled one pcb yet. When I try to fit 2sc5200 (to-264) and some similar transistors (including mt-200) as output, but i saw that layout's leg distance was wider to fit. I checked original TIP3055's leg space dimensions in datasheet and I see that it is match to those I had to try. My measured two leg distance on pcb is about 7mm.TIP3055 in datasheet and other devices i tried are about 5.5mm.
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Old 29th November 2011, 07:44 PM   #335
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i used TOP3 package, since that's what i can get 2n3055's in except for TO3.
but i can change to TO-264 no problem. i prefer 2sc5200/2sa1943 myself.

pinning is the same tough.

if you've found other problems (such as packages, clearance etc. not another redesign), let me know and i will correct them. attached TO-264 version.
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Last edited by powerflux; 29th November 2011 at 08:03 PM.
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Old 29th November 2011, 08:20 PM   #336
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Quote:
Originally Posted by powerflux View Post
i used TOP3 package, since that's what i can get 2n3055's in except for TO3.
but i can change to TO-264 no problem. i prefer 2sc5200/2sa1943 myself.

pinning is the same tough.

if you've found other problems (such as packages, clearance etc. not another redesign), let me know and i will correct them. attached TO-264 version.
Thank you for fast response and excellent pcb design of course. I will notice if I face any possible issue.

Last edited by terranigma; 29th November 2011 at 08:23 PM.
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Old 30th November 2011, 07:30 AM   #337
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by terranigma View Post
Hello Elvee,

I wonder that how this topology sensitive for faster output transistors (10~80 mhz). You pointed already that C12 should be 820pF for faster devices.
It has been tested with relatively fast transistors, such as the BDY58 (Ft=30MHz).
C11 will probably become compulsory, but it is not a certitude: it will also depend on the driver and phase splitter transistors, and the wiring.
The wiring influence becomes more and more important when the Ft of OP transistors is increased

Quote:
Have you any suggesting indicator for sure that amplifier is healthy or not??
The first elementary test is to connect an oscilloscope to the output, and look for any HF parasitic signal.
This has to be done with a load, and with a low frequency sinusoidal signal of large amplitude (1KHz f.e.).
This is because parasitic oscillations can have multiple causes, and you need to sweep the whole current range for both halves of the PP to be certain not to miss something.
An oscillation could manifest itself by the thickening of the trace on the positive peaks of the waveform for example.
If you want to go deeper, you can inject a squarewave signal, and look at the transitions: you will be able to detect marginal stability issues, even if the amplifier is not oscillating: this will typically generate a prolonged ringing after each transition.
You have to be sure to feed a clean squarewave in the first place: if you use a relatively long, mismatched cable, this will create reflections that are almost undistinguishable from ringing.
I have given the schematic of a simple, cheap and clean squarewave generator here: ♫♪ My little cheap Circlophone© ♫♪

Quote:
And bridged configuration.. has topology any drawback regarding to two amplifiers as bridged configuration? In this case, can we avoid source signal ground connected to each amplifier regarding to use of balanced signal
The bridged configuration has not been tested, but there is no reason it wouldn't work.

You could feed a balanced signal that way, but be aware that any common-mode signal or offset will eat up output dynamic.
With a well balanced capacitively coupled signal, this should work perfectly.
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Old 30th November 2011, 11:44 AM   #338
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@Elvee

When I asking, I was aware that your early posts regarding same issue. In fact, as an average diyer, I have no facility for measuring Mhz level signals. I think it is the best to ask for a favor from a oscilloscope owner from my around.

Thank you.
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Old 30th November 2011, 02:14 PM   #339
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Quote:
Originally Posted by Elvee View Post
An oscillation could manifest itself by the thickening of the trace on the positive peaks of the waveform for example.
Sorry for misunderstood. Does this mean, I can trap a HF oscillation even with analyzing a 1khz sinus or square waveform?
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Old 30th November 2011, 02:52 PM   #340
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by terranigma View Post
Sorry for misunderstood. Does this mean, I can trap a HF oscillation even with analyzing a 1khz sinus or square waveform?
Yes and no: you need "something" to observe the trace, and the something must have a sufficient bandwidth, at least several MHz.
This rules out sound card based oscilloscopes for instance.

Reliably detecting an oscillation by other means would be difficult.
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