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Old 18th April 2005, 09:51 PM   #1
NITRO is offline NITRO  Turkey
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Question LM3886 Quiescent current

Hi all;
I just made an amplifier with two LM3886 in parallel configuration
with servo circuit.But i have some thermal problems.Circuit draws 200 mA quiescent current from each rail.With the +/- 33 V of supply voltage idle thermal dissipation exceeds 13 Watts.I think that it's not a normal.Anybody encountered this problem before?
Waiting your comments.
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Old 18th April 2005, 10:00 PM   #2
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Most likely cause is oscillation.
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Old 18th April 2005, 10:23 PM   #3
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Can you make one LM3886 work properly?

How does your design look like? Is it taken from AN-1192?

How much DC offset do you get?

Which value have the resistors from each output? 0.1, 0.22 or 0.33 ohms?
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Old 20th April 2005, 06:20 PM   #4
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Hi Nitro

The max. idle currnet for ONE LM3886 is 80 mA (and I have never really seen it this high) so for two it should max. be 160 mA + additional circuits.

Either you have to much DC-offset (if your DCServo is working OK you should not have this problem.) or you have osc.

Having worked with 4 x LM3886 in bridged/paralle configuration I typicall ended up with around 250 mA idle current so your 200 mA for just two LM3886 seems "wrong".

Have fun

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Old 20th April 2005, 10:06 PM   #5
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Hi Thomas

I'm still making modifications on the circuit from yesterday, and finally got 150mA at idle.I think that it is a good value for two ics.Maybe i can lower this current 100-200 mA less, stil trying.Actually not a high value for home use but im gonna use this at car so the dissipation must be low.

Thanks for all replies.

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