LM3886 Quiescent current

NITRO · 18th April 2005, 09:51 PM

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.

pinkmouse · 18th April 2005, 10:00 PM

Most likely cause is oscillation.

peranders · 18th April 2005, 10:23 PM

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?

tlmadsen · 20th April 2005, 06:20 PM

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

Thomas

NITRO · 20th April 2005, 10:06 PM

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.

Türker

18th April 2005, 09:51 PM	#1
NITRO diyAudio Member Join Date: Jan 2004 Location: istanbul	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.

18th April 2005, 10:00 PM	#2
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	Most likely cause is oscillation. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

18th April 2005, 10:23 PM	#3
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	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? __________________ /Per-Anders (my first name) or P-A as my friends call me Tube Buffered Gainclone in work \|Thread

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20th April 2005, 06:20 PM	#4
tlmadsen diyAudio Member Join Date: Aug 2003 Location: Roskilde - The vikingships	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 Thomas

20th April 2005, 10:06 PM	#5
NITRO diyAudio Member Join Date: Jan 2004 Location: istanbul	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. Türker

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