LM1875 PCB Layout

mangrovejack · 4th July 2005, 02:31 AM

Hi Guys,

I'm currently building a 5 channel chipamp and have finally come up with a PCB design (took me a while to learn how to use Eagle).

I've attached the schematic and board for your perusal. Could you guys please go through my PCB layout and give me any hints and tips on ways to improve it.

Keep in mind that I'm planning on eventually having 5 of these PCB's side by side so the design is intended to be as small as possible long the width.

I've based my schematic on carlosfm's snubber design and Nationals datasheet schematic and will be using his design also for the power supply.

Amy I missing anything as I have seen in a few schematics for chipamps that they have around 2.2k ohm resistor inline with the positive input to the chip. What is this for and do I need it?

Thanks.

mangrovejack · 4th July 2005, 02:33 AM

Here's the board layout:

homer09 · 4th July 2005, 04:48 AM

Quote:

Originally posted by mangrovejack

Amy I missing anything as I have seen in a few schematics for chipamps that they have around 2.2k ohm resistor inline with the positive input to the chip. What is this for and do I need it?

Thanks.

this is a "safety" resistor used in series with positive input. it is used to reduce dc offset, or protect against some dc incoming mostly on power up/down. with a cap at the input i think you could get away without that resistor.

metal · 4th July 2005, 05:43 AM

Hello

Can you please upload eagle files you are working on + LM1875 Library.

Thanks

Tekko · 4th July 2005, 07:31 AM

Output2 should be going to ground and Output1 remains on the opa output.

mangrovejack · 4th July 2005, 07:34 AM

Quote:

Originally posted by Tekko
Output2 should be going to ground and Output1 remains on the opa output.

I'm not sure what you mean by that?

Maybe I should have explained why I have two "outputs". It was because one wire pcb terminal wouldn't be stable enough (only one leg to solder), so I thought I'd just use a double one ant leave one output empty.

<Edit>Ah, I understand what you mean now. I'm getting the output ground from the star ground at the caps, and not on the PCB to reduce the possibility of hum.</edit>

mangrovejack · 4th July 2005, 07:37 AM

Sorry Tekko, I edited my post as you were sending yours.

Tekko · 4th July 2005, 07:38 AM

Oops

I deleted my last post.

mangrovejack · 5th July 2005, 02:04 AM

So no-one can see any problems with this layout? That's great then, as I can start making the PCB and testing it out.

I'll report back the results when I'm done.

metal · 5th July 2005, 06:06 PM

Hello

Can you please upload schematic, PCB, and LM1875 library

4th July 2005, 05:43 AM	#4
metal diyAudio Member Join Date: Jan 2004	Hello Can you please upload eagle files you are working on + LM1875 Library. Thanks __________________ any way, finally...

5th July 2005, 06:06 PM	#10
metal diyAudio Member Join Date: Jan 2004	Hello Can you please upload schematic, PCB, and LM1875 library __________________ any way, finally...

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4th July 2005, 07:31 AM	#5
Tekko diyAudio Member Join Date: Jan 2005	Output2 should be going to ground and Output1 remains on the opa output.

4th July 2005, 07:37 AM	#7
mangrovejack diyAudio Member Join Date: Dec 2004 Location: Brisbane	Sorry Tekko, I edited my post as you were sending yours.

4th July 2005, 07:38 AM	#8
Tekko diyAudio Member Join Date: Jan 2005	Oops I deleted my last post.

5th July 2005, 02:04 AM	#9
mangrovejack diyAudio Member Join Date: Dec 2004 Location: Brisbane	So no-one can see any problems with this layout? That's great then, as I can start making the PCB and testing it out. I'll report back the results when I'm done.

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