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Old 22nd June 2011, 11:06 AM   #51
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Quote:
Originally Posted by hurtz View Post
Yep, but since pin 11 is not connected, it doesn't matter and I wanted to give the input line more room.
Wait isn't pin 7 the ground pin on the board? where at least the dissipated power flows through?
no! Pin 7 does not carry much current and a reasonable track with, that can be home etched easily would be fine. Same goes for the input pins.
Touching unused pins with tracks is bad style, if not worse. Cutting of unused pins to have more room on the pcb is a really desperate measure.
I think you have painted yourself into a corner.
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Old 22nd June 2011, 12:51 PM   #52
hurtz is offline hurtz  Germany
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Actually apart from pin 11 no pin has to be clipped, or is being touched, and for pin 11 I could move the parts down a little that no clipping would be necessary, but this way Cc and Cin are closer to the input pin
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Old 22nd June 2011, 01:28 PM   #53
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http://img155.imageshack.us/img155/5302/ampv43.png
so pin 2,6,11 have vanished from your pcb by magic?
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but this way Cc and Cin are closer to the input pin
I find this design somewhat strange, for example using wider track widths at the input pins than at the amps output etc.

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Old 22nd June 2011, 01:54 PM   #54
hurtz is offline hurtz  Germany
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Yes I have removed the Pads for those pins, but when drilling everyone can decide whether he wants to drill holes for them or clip them. As for pin 11, the point-to-point method of wiring is considered to be OK, but clipping a pin thats not in use to decrease track length is not?
Also most of the tracks were made as big is possible, if only to save on etching solution. The Output-track has a with of 1.27mm at the moment.

And please cut me some slack, this is the first PCB I've ever designed...
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Old 22nd June 2011, 02:11 PM   #55
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I've noticed your progress and you certainly deserve lots of praise for it!
nevertheless..
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Old 22nd June 2011, 02:39 PM   #56
marce is offline marce  United Kingdom
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The small value decoupling caps wont do much as they require a short leads and a small loop, with the main ground going from the chip back to the star then the ground from the star to the caps the track inductance will be dominant, reducing the effective frequencys they work at. The small caps should be next to the pins and the tracks (power and ground) as short as possible.
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Old 22nd June 2011, 02:43 PM   #57
infinia is offline infinia  United States
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Originally Posted by Juergen Knoop View Post
I've noticed your progress and you certainly deserve lots of praise for it!
nevertheless..
+1
agree with most other comments ie like leaving off IC lead pins.
youre right about light IC ground currents, BUT decoupling need low inductance trace widths to chip amps internal s.
TIP > one or two well placed wire jumpers can make or break a single sided layout. used on signals or outputs can free up valuable routing area.
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Old 22nd June 2011, 03:23 PM   #58
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Whoever said the datasheet is your friend, was lying, at least in this case.
The national datasheet is kind of a disgrace in showing only half an amp without all the components to deal with its non-ideal qualities.
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Old 22nd June 2011, 04:12 PM   #59
infinia is offline infinia  United States
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Originally Posted by digits View Post
Whoever said the datasheet is your friend, was lying, at least in this case.
The national datasheet is kind of a disgrace in showing only half an amp without all the components to deal with its non-ideal qualities.
well the OP started with a design based partly on marketing speak ie minimal parts gain clone. He was then directed to NS data sheets where an engineer still needs to be able to read between the lines to seperate the wheat from the chaff so to speak, but it's all in there. All chip amps have to deal with the same physics or as you say non-ideal qualities. I'd rather include more parts for a robust amp design than some other thing with all it's limitations.
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Old 22nd June 2011, 04:24 PM   #60
hurtz is offline hurtz  Germany
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Quote:
Whoever said the datasheet is your friend, was lying, at least in this case.
The national datasheet is kind of a disgrace in showing only half an amp without all the components to deal with its non-ideal qualities.
And I was close to thinking I'm just to stupid for this

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TIP > one or two well placed wire jumpers can make or break a single sided layout. used on signals or outputs can free up valuable routing area.
Well, I can't talk about "well" placed, but the capacitor-loop is definitely shorter now.

Quote:
I've noticed your progress and you certainly deserve lots of praise for it!
nevertheless..
Thanks I'm still working on the nevertheless...

Still, clipped pin 11 stays, if only for individualistic sake.

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