LM386 RF suppression

DrFrankenstein · 27th April 2006, 08:44 AM

I built the LM386 utility amplifier based off the circuit provided in the manufacturers PDF file and am experiencing radio interferance. I don't know if it's short wave or what cuz there are these german people...some times French or British...or worst of all religious sermons!

Anyway, how does one filter out this gook?

tlmadsen · 27th April 2006, 12:54 PM

LR-circuit on the output and 220pF across the two inputs (+/-) of the LM3886.

Thomas

mctylr · 29th April 2006, 06:11 PM

See page 6 of National's LM386 datasheet.

For the lazy:
http://www.national.com/ds/LM/LM386.pdf

DrFrankenstein · 2nd May 2006, 06:41 AM

Hey thanks for the replies and help, I knew it was going to be a simple capacitor filtering solution but none of the values I tried worked. Do I really need to go so far as to adding the LR circuit though?

tlmadsen · 4th May 2006, 08:43 AM

The need of the LR-circuit is very dependent on the load (including cable) that the amplifier sees, so start without and see how it works. A small powerresistor will actually have the same effect (say 0R2/5 w)

Have fun

Thomas

27th April 2006, 08:44 AM	#1
DrFrankenstein Banned Join Date: Apr 2006 Location: Frankensteins Castle	LM386 RF suppression I built the LM386 utility amplifier based off the circuit provided in the manufacturers PDF file and am experiencing radio interferance. I don't know if it's short wave or what cuz there are these german people...some times French or British...or worst of all religious sermons! Anyway, how does one filter out this gook?

29th April 2006, 06:11 PM	#3
mctylr diyAudio Member Join Date: Nov 2005	Use the datasheets See page 6 of National's LM386 datasheet. For the lazy: http://www.national.com/ds/LM/LM386.pdf

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27th April 2006, 12:54 PM	#2
tlmadsen diyAudio Member Join Date: Aug 2003 Location: Roskilde - The vikingships	LR-circuit on the output and 220pF across the two inputs (+/-) of the LM3886. Thomas

2nd May 2006, 06:41 AM	#4
DrFrankenstein Banned Join Date: Apr 2006 Location: Frankensteins Castle	Hey thanks for the replies and help, I knew it was going to be a simple capacitor filtering solution but none of the values I tried worked. Do I really need to go so far as to adding the LR circuit though?

4th May 2006, 08:43 AM	#5
tlmadsen diyAudio Member Join Date: Aug 2003 Location: Roskilde - The vikingships	The need of the LR-circuit is very dependent on the load (including cable) that the amplifier sees, so start without and see how it works. A small powerresistor will actually have the same effect (say 0R2/5 w) Have fun Thomas

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