I need .200 ohms to be placed at the output of a power opamp(lm3886)
I'm thinking of paralleling 5x 1ohm 0.6w metal film to get the desired resistance. Thoughts?
Thanks for the help.
Edit: forgot to mention that all the resistors are of 1% tolerance.
This is a sample schematic of the amp.
I'm thinking of paralleling 5x 1ohm 0.6w metal film to get the desired resistance. Thoughts?
Thanks for the help.
Edit: forgot to mention that all the resistors are of 1% tolerance.
This is a sample schematic of the amp.
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Wirewound has higher inductance - could eventually be a problem if the resistor is inside the feedback loop.
Metal film paralleled has even lower tolerance and low inductance, so probably better (correct me if i'm wrong!)
Metal film paralleled has even lower tolerance and low inductance, so probably better (correct me if i'm wrong!)
You'll likely be fine on music but if you play full-level test tones through your amp into a 4R load you may exceed the power rating of those 0.6W resistors. At least until the Spike protection kicks in.
Sure it does, but I figure under worst case conditions you might get as much as 1ARMS flowing through each. Which is 1W apiece. But if you don't plan on using test tones you'll be fine.
For resistors of the same value in parallel, you can add the power ratings of the individual resistors to get the overall power. However, the power rating given for a single resistor assumes that it is in free air, and if you bundle the resistors together they heat each other and the overall power must be derated. So it's best to keep the resistors physically spread out by some reasonable distance. I suppose that the power rating for a single resistor has to assume some range for ambient temperature, but I don't know offhand how that is done.
Tom
Tom
The load will get almost 20 times the power of the .2 ohm resistor. So at 60 watts of continuous power he will hit the resistors limit. It will not be exact as the resistors although quite close to each other in value will not be exactly the same. Also the absolute value will differ slightly.
The other issue is that a 4 ohm loudspeaker load can dip to 2 ohms at some frequencies.
Thus playing music the resistors might be overloaded on say 180 watts of Techno-pop!
Of course the amplifier cannot deliver that much power, so no real worries.
One other note is that metal film resistors do not have much surge capacitor above the rated wattage. But that is not an issue here.