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Old 8th February 2006, 03:20 PM   #21
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Wisdom ? Why ? Try to tell to The God, that human body is " too complicated " and that he can make it more simply...He will thinking about it and result will be ameba...
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Old 8th February 2006, 03:28 PM   #22
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Quote:
Originally posted by thalis
Obviously, they are Wise.
So, it’s not called funny, dear Upupa, its called wisdom. Wisdom gives (always did and always will) simple and powerful answers to ‘complicated’ questions.
[snip]

Yes indeed. For every difficult, complicated and complex problem there is a simple, easy to understand wrong answer.

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Old 8th February 2006, 03:31 PM   #23
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Yes, amen...
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Old 8th February 2006, 04:12 PM   #24
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Hi Mad_K

Why do you do not use the minus rail as input ground?

The way you have , the input ground is referenced to the the positive rail and the source of the mosfet is referenced to the minus rail, but the voltage that the mosfet "see" and amplifies , is the voltage between gate and source...

With your grounding arrangement the PSRR will be very poor...
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Old 8th February 2006, 04:31 PM   #25
lohk is offline lohk  Europe
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Hi Mad_k,

isn't the output cap drawn reversed in your schematic? I should have plus to gound.
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Old 8th February 2006, 05:40 PM   #26
Mad_K is offline Mad_K  Norway
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Quote:
Originally posted by lohk
Hi Mad_k,

isn't the output cap drawn reversed in your schematic? I should have plus to gound.

You're absolutely right, thanks. Attached is the corrected schematic.
Attached Files
File Type: pdf ota3,5r0.sch.pdf (52.6 KB, 717 views)
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Old 8th February 2006, 06:00 PM   #27
Mad_K is offline Mad_K  Norway
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Quote:
Originally posted by Tube_Dude
Hi Mad_K

Why do you do not use the minus rail as input ground?

The way you have , the input ground is referenced to the the positive rail and the source of the mosfet is referenced to the minus rail, but the voltage that the mosfet "see" and amplifies , is the voltage between gate and source...

With your grounding arrangement the PSRR will be very poor...
source follower:

FET amplifier in which signal is applied between gate and drain with output taken between source and drain. Also called "common drain."
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Old 8th February 2006, 06:46 PM   #28
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Quote:
Originally posted by Mad_K


source follower:

FET amplifier in which signal is applied between gate and drain with output taken between source and drain. Also called "common drain."
Do some home work, please:

http://www.eie.polyu.edu.hk/~ensurya...h2/Fig2-18.jpg

http://www.ee.bilkent.edu.tr/~aytur/.../labs/exp6.pdf
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Old 8th February 2006, 07:54 PM   #29
thalis is offline thalis  Greece
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Dear Yan, this can also be true.
In Greek we have different words for ‘simple but probably effective’, and for ‘dangerously simplified’, but unfortunately the English translation is the same: ‘Simple’.
In my opinion many of these little circuits are simple and effective if someone has the right speaker: sensitive and of smooth impedance (which two quantities are regarded as speaker qualities, in my way of thinking, btw). Then they can prove to be sonically even better from more complicated, respected, and well measuring designs. As we all know, there are many people who have such experiences, and such simplicity can be considered as a certain ‘philosophy’ in sound reproduction. All these people have the right to experiment, listen, like what they listen, post their findings without having to deal with questions like “how can this play good music, so simple as it is, with such a distortion figure etc.?” again and again. In the same time and as I have seen, all these don’t get into other forum discussions (regarding more complicated designs) protesting or demonstrating their different point of view, saying for instance ‘why do you build such a 4 stage circuitry, why not cut 2 stages’, or ‘how can this work with so many parts?’.
In general, I presume that these people know better that Hi-Fi isn’t a one-way street, nor is it determined from specific specs, so I (again) presume they perhaps know better how to choose an appropriate way (since they don’t know of only one) to satisfy their needs.
Now, about simplicity and complication: Even for this simple matter, of someone’s right and pleasure to post here his findings and have a conversation (given his simplistic approach and likings) and get on-topic comments and disagreements like tube-dude’s and lohk’s, and nothing else, we people have to complicate things enough to loose our motives.
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Old 8th February 2006, 08:12 PM   #30
Mad_K is offline Mad_K  Norway
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Yes, I'm well aware that's the normal way to connect it. I was thinking of the sentence I posted earlier, as this is the way it is descibed in my book "Microelectric Circuits". I would very much appreciate a lesson in how this affects the PSRR, and AC signal current loop, in the mean time I will redraw the schematic to comply with the normal way of thinking.
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