LM384: Output noise issue

Wu JW

Part Number: LM384

Hi, Team,

My customer met some issue for LM384, could you help check it?

They found the noise was very big by using LM384, which cover the original audio signal . If we remove the LM384, the audio signal is clean. We try to use the battery to give the power supply, the noise still very big. Could you give some suggestion for this? Thanks!

The SCH as followed:

The input and output signal.

over 7 years ago

0 kai klaas69 over 7 years ago

Guru 140200 points

Hi Wu,

looks like the noise is superimposed on the input signal. Does the noise at output of LM384 dissapear if you connect the left side of R93 to GND?

Some additional tips: R100 should be 2R7 not 2R2. C79 should be 100n/50V/X7R or better a foil cap. And put 1n/NP0 in parallel to R95.

What speaker do you connect to the output? Is there a long cable?

Kai

0 Ivan Salazar over 7 years ago

TI__Guru** 110125 points

Hi Wu,

The noise is present at the input of the amplifier. Have you tried to remove R93 or connecting it to GND? Is there any change by doing this? Also a single capacitor on Bypass pin is recommended, have you tried that?.

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

0 Ivan Salazar over 7 years ago

TI__Guru** 110125 points

Wu,

It has been almost a week since last communication. Can we consider this as closed?

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

0 Wu JW over 7 years ago in reply to Ivan Salazar

TI__Intellectual 2935 points

Hi, Ivan,

Thanks for your kindly support! The issue is closed.

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LM384: Output noise issue