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Old 31st October 2002, 04:40 AM   #1
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Default x-bosoz

Here is a modification to update the BOSOZ.
Please note that there is no need of output capacitors.

Any comment will be appreciated.
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File Type: jpg x-bosoz-1.jpg (39.0 KB, 5337 views)
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Old 31st October 2002, 06:51 AM   #2
Henrik is offline Henrik  Denmark
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Hi Peter

It looks pretty much Nelsons patent.
I think You need some inputresistors, or you have to trust the outputimpedance of signalsource.

May be the value of R8 is too high, try to short it, and add some more feedback.

Could You explain some more of Your point of views on this one.

I would like to do some sims, but it will be in the evening.

Could be an interting project.



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Old 31st October 2002, 08:07 AM   #3
Henrik is offline Henrik  Denmark
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If You take away the folded cascodes, You end up with a simple XBOSOZ or a XSOZ for that matter.
As I remember, Nelson once talked about these folded casodes, and I thik his reason to implant these was to acheve better linearity at frequences higer than the audioband, >100kHz.
So do we need them at all?
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Old 31st October 2002, 02:36 PM   #4
eLarson is offline eLarson  United States
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Quote:
Originally posted by Henrik
If You take away the folded cascodes, You end up with a simple XBOSOZ or a XSOZ for that matter.
As I remember, Nelson once talked about these folded casodes, and I thik his reason to implant these was to acheve better linearity at frequences higer than the audioband, >100kHz.
So do we need them at all?
I'm not sure how high it stays linear, but perhaps it helps keep AM (medium-wave, in Europe? 550kHz to 1600 kHz) band signals from producing modulation products that end up in the audio band?

Erik
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Old 31st October 2002, 06:47 PM   #5
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With the folded cascode the differential pair sees a constant voltage then the bandwith become better and the distorsion low.
Not to mention the output swing.
Sure it helps drive such difficult loads like some x-son of zen back in the x-soz thread.

Cheers
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Old 31st October 2002, 11:36 PM   #6
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I would agree the second cascoded stage is not so important for small signal, audio frequency and low gain application. In this circuit, I intended to level shift the output signal to eliminate the potential dc voltage to a quite low value. This can be done by adjusting the potentiometers VR1 and VR2 in the circuit. Thus, the output capacitor shown in the original bosoz project can be kicked away. I don't like signal capacitors.

In this circuit, the original bosoz parts is still remained in and only two p mosfet and three 750 Ohm resistors are added. It would be quit easy to modify the original bosoz, if you had constructed one. I constructed a bosoz without pcb and preserve some space to upgrade.

I don't like feedback either. I would take out the resistors, R4 and R10.

I hope somebody can help to analyze performances of this circuit.

Thanks.
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Old 1st November 2002, 12:30 PM   #7
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When I played around with this circuit , some months ago, I did notice that it didn't work if R10 and R4 were out.

...but I may be wrong.
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Old 4th November 2002, 12:06 AM   #8
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Here are my simulations.
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File Type: jpg x-bosoz-1-output with feedback-2.jpg (57.1 KB, 4550 views)
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Old 4th November 2002, 12:08 AM   #9
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Another drawing
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File Type: jpg x-bosoz-1-output without feedback.jpg (64.0 KB, 5374 views)
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Old 4th November 2002, 02:21 PM   #10
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Interesting , Peter .
What do you think to drive it balanced?
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