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Chip Amps Amplifiers based on integrated circuits

schem for LM1875 PCB
schem for LM1875 PCB
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Old 29th October 2008, 09:05 PM   #1
missieek is offline missieek  Poland
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Join Date: May 2008
Default schem for LM1875 PCB

I've bought some time ago this PCBs for LM1875 chips but I dont't have a scheme for this circuit. Could anyone help me? In application note there's nothing similar.
They are places for eight diodes, two electrolitic capacitors and three resistors. What value of these parts to use?
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Old 29th October 2008, 09:31 PM   #2
pacificblue is offline pacificblue  Germany
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Join Date: May 2008
Default Re: schem for LM1875 PCB

Originally posted by missieek
In application note there's nothing similar.
Yes, there is. The place of the uppermost resistor in your photo is for R4, directly below the IC there is R3 and below that R2. The capacitors are C6 and C7, all derived from the first page of the datasheet.

As you can see, the datasheet shows more components. All of them have their purpose. Most of them have to do with safety.

Your PCB is the minimum configuration that is able to work at all. On your PCB there is no blocking at the input that could protect the IC from dangerous signals. Neither is there a Zobel circuit at the output to prevent the amp from oscillating. DC protection is also not provided on board.

Conclusion: If you use it at all, use it only with a small power supply and a robust speaker to bring the potential for damage down. Or add all the missing components off board.
If you've always done it like that, then it's probably wrong. (Henry Ford)
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