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The LM386 TI applications notes page 11 show an amplifier. Would like to use this chip with complete isolation of the output speaker and with the addition of an isolated input speaker. Am using impedance matching transformers on input and output for speaker isolation from the power supply. Should the 10 mfd shown be polarized?

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    \$\begingroup\$ Please edit your question with a link to the app note in question. While you're at it, a schematic showing how you propose to add a transformer would be nice. \$\endgroup\$ – TimWescott Dec 26 '18 at 22:31
  • \$\begingroup\$ If you're going to tie one end of the transformer to ground then you need a cap between the LM386 output and the transformer. The LM386 output cannot go outside the rails, so it needs a blocking cap to drive something like a speaker or transformer primary. The cap doesn't need to be polarized, but a polarized cap is perfectly suitable, and possibly the least expensive solution. \$\endgroup\$ – TimWescott Dec 26 '18 at 22:34
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Yes, the 10µF capacitor between pins 1 and 8 can be polarized, but it doesn't have to be. If you use a polarized capacitor, have the negative side on pin 8.

This will give you a gain of 200. If you want a different gain, you need to add a series resistor.

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