Lme49830 - Page 3

nickarsow · 16th February 2009, 04:12 PM

Hi Segran,
I'll take your advice and will separate the two grouns.
More , the 10R resistor will be placed between them.
A question:
Could I still use poligons for both grounds?
Regards
Nick

nickarsow · 16th February 2009, 04:14 PM

P.S. - to Segran
By the way - what's your opinion about the PCB concept?
Regards
Nick

Segran · 16th February 2009, 09:27 PM

It looks OK, but I wouldn't use a ground plane for an audio amplifier PCB. If I did, I would use it for Signal GND, not Power GND.

To avoid oscilations I suggest you put the Gate resistors for the MOSFET's directly on the Gate's, either on the separate PCB for the output stage or directly P2P.

nickarsow · 17th February 2009, 08:35 AM

Dear Segran,
I'll remove the gate resistors along with gate to gate resistor.
Please advice where to link bypass OpAmp capacitors - to signal ground or to power ground as the currents drawn from the OpAmp are too small?
Regards
Nick

AndrewT · 17th February 2009, 10:28 AM

the decoupling caps on opamps, chipamps and amplifiers are there to reduce glitches & spikes in the power supply when currents turn on or off suddenly.
These glitches and spikes are not clean. They must never be taken through a clean return or shared with another clean signal.

nickarsow · 17th February 2009, 10:36 AM

Thanks Andrew,
I know all this , but the question was where to ground small electrolytic capacitors which are filtering the supply of LM833 (LME49720)?
Should they be connected to AGND or PGND?
Thanks
Nick

nickarsow · 17th February 2009, 10:38 AM

Dear All,
Here are the new gerber files with clean AGND and PGND separated by 10R resistor R100.
Nick

AndrewT · 17th February 2009, 10:41 AM

do not connect dirty lines to signal ground.

nickarsow · 17th February 2009, 10:54 AM

The new gerbers shown above are with clean AGND - all el.capacitors are tied to PGNS. The two ground are connected via 10R.
Thanks
Nick

Segran · 17th February 2009, 12:48 PM

Hi Nick,

your changes fixes noise (spikes) coming in from GND. Personally I would get rid of the power plane you have on the top layer as well, since it's connected to PGND. I have seen spikes entering the op amps through capacitive coupling from noisy power ground planes.

17th February 2009, 10:28 AM	#25
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	the decoupling caps on opamps, chipamps and amplifiers are there to reduce glitches & spikes in the power supply when currents turn on or off suddenly. These glitches and spikes are not clean. They must never be taken through a clean return or shared with another clean signal. __________________ regards Andrew T.

17th February 2009, 10:41 AM	#28
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	do not connect dirty lines to signal ground. __________________ regards Andrew T.

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16th February 2009, 04:12 PM	#21
nickarsow diyAudio Member Join Date: Feb 2009	Hi Segran, I'll take your advice and will separate the two grouns. More , the 10R resistor will be placed between them. A question: Could I still use poligons for both grounds? Regards Nick

16th February 2009, 04:14 PM	#22
nickarsow diyAudio Member Join Date: Feb 2009	P.S. - to Segran By the way - what's your opinion about the PCB concept? Regards Nick

16th February 2009, 09:27 PM	#23
Segran diyAudio Member Join Date: Sep 2008	It looks OK, but I wouldn't use a ground plane for an audio amplifier PCB. If I did, I would use it for Signal GND, not Power GND. To avoid oscilations I suggest you put the Gate resistors for the MOSFET's directly on the Gate's, either on the separate PCB for the output stage or directly P2P.

17th February 2009, 08:35 AM	#24
nickarsow diyAudio Member Join Date: Feb 2009	Dear Segran, I'll remove the gate resistors along with gate to gate resistor. Please advice where to link bypass OpAmp capacitors - to signal ground or to power ground as the currents drawn from the OpAmp are too small? Regards Nick

17th February 2009, 10:36 AM	#26
nickarsow diyAudio Member Join Date: Feb 2009	Thanks Andrew, I know all this , but the question was where to ground small electrolytic capacitors which are filtering the supply of LM833 (LME49720)? Should they be connected to AGND or PGND? Thanks Nick

17th February 2009, 10:54 AM	#29
nickarsow diyAudio Member Join Date: Feb 2009	The new gerbers shown above are with clean AGND - all el.capacitors are tied to PGNS. The two ground are connected via 10R. Thanks Nick

17th February 2009, 12:48 PM	#30
Segran diyAudio Member Join Date: Sep 2008	Hi Nick, your changes fixes noise (spikes) coming in from GND. Personally I would get rid of the power plane you have on the top layer as well, since it's connected to PGND. I have seen spikes entering the op amps through capacitive coupling from noisy power ground planes.

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