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Chip Amps Amplifiers based on integrated circuits

An open source layout for the lm3886 ?
An open source layout for the lm3886 ?
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Old 27th April 2018, 12:57 PM   #11
00940 is offline 00940  Belgium
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Ok, first revision.

Now with a signal groundplane on top and a complete power groundplane on bottom. The input filter is also closer to the input gnd.
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Old 28th April 2018, 01:06 AM   #12
bozoc is offline bozoc  Croatia
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Like the last layout, I would still try to put that C6 more to the right side (if you plan to use nichicon muse).
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Old 28th April 2018, 05:32 AM   #13
Mark Whitney is offline Mark Whitney  Netherlands
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Remove the PGND plane from under the input and feedback traces/parts. The AGND plane goes under the input and feedback circuits only.

Add the option of a Hum Breaking Resistor between the output GND and AGND. This will
help when you use multiple boards connected to a single transformer.

The LM3886 inputs are high impedance, keeping these traces short will prevent hum.
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Old 28th April 2018, 09:13 AM   #14
00940 is offline 00940  Belgium
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- shorter input tracks are possible if I move the RF filter before the input cap. I'll have a try.
- a ground breaker resistor... I can add that.
- removing the power ground plane around the inverting pin could help. If I'm removing it all around the input, we're pretty much back to the first layout and we're wasting some copper.
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Old 28th April 2018, 09:26 AM   #15
bozoc is offline bozoc  Croatia
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I might be mistaken but given the LM3886, removing the PGND under feedback network might do more harm than good.
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Old 28th April 2018, 09:32 AM   #16
nigelwright7557 is offline nigelwright7557  United Kingdom
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You can save a couple of dollars if you replace screw terminals with 1mm pcb pins.
A soldered joint is better than a terminal block.
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Old 28th April 2018, 09:46 AM   #17
bozoc is offline bozoc  Croatia
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Multi strand soldered wire is prone to breakage and is not a very reliable way to connect the wire to PCB, there needs to be a strain relief of some sorts or hot glue/silicone acting as a support and that is a mess.
Terminals and crimped connectors are much more reliable over time.
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Old 28th April 2018, 10:02 AM   #18
cspirou is offline cspirou  United States
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BTW, BrianGT of chipamp.com has open up his boards to the public domain.

my first try at a LM3886 layout, any comments/suggestions?
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Old 28th April 2018, 10:37 AM   #19
levistubby is offline levistubby  United Kingdom
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Quote:
Originally Posted by bozoc View Post
Multi strand soldered wire is prone to breakage and is not a very reliable way to connect the wire to PCB, there needs to be a strain relief of some sorts or hot glue/silicone acting as a support and that is a mess.
Terminals and crimped connectors are much more reliable over time.

There should be no need for strain relief in situations where the cables don't move. Unless of course the cable are very heavy, which will not be the case here.
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Old 28th April 2018, 11:58 AM   #20
00940 is offline 00940  Belgium
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Nothing prevents someone to solder wires directly in the holes made for screw and faston terminals.

As for the chipamp PCB... Well, it's missing most of the stability components and it's not a particularly good layout imo.

For the ground plane under the feedback network. Usually, the problem is capacitive coupling at the inverting pin. But considering the length of the legs of the IC, it's probably not a big deal here, as it can be with fast opamps.
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