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LM386: Omitting output RC

Zotin Khuma
Prodigy 120 points
Part Number: LM386

 Vcc = 12V regulated, Speaker Z = 8 ohms. Basic minimal configuration with Gain = 20

Signal = short bursts of ~300 Hz with high harmonics content. No music or speech. Sound quality not important.

Resistor of 5-10 ohms to be placed in series with the speaker (to reduce dissipation and supply drain)

Does this configuration still need the usual output RC network for stability?

  • 0
    TI__Guru** 108765 points
    Hi Zotin,

    Welcome to e2e.
    It is recommended to use the RC network, this will avoid any possible instability caused by parasitic capacitance that could be generated by output traces or cables.
    One thing you could try is to leave it as an option (place the component footprints). This way you can test performance without the RC network and place the components if they're necessary.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Ivan Salazar
    Prodigy 120 points
    Thanks for the reply. I was hoping that the resistor in series with the load would be enough to obviate any possibility of instability. Obviously that's not the case.

    Even if one build is initially stable without the RC network, there's no assurance that future similar or identical applications will also be stable due to component tolerances and aging, variations in external factors, etc.

    Another thing is that, once the component footprints are included on the PCB, there's no gain in PCB real estate and the two less-than-one-cent parts might as well be fitted right away.

    Anyway, your reply was helpful as it tells me that it wouldn't be wise to leave out the RC combo. Thanks again.