Resistor Noises: How to reduce them
I just figured if we parallel n exact same resistors together,
we will get 1/n times the noise power of each resistor. For example, we we want 1 ohm resistance, we can parallel 2 pieces of the 2ohm resistors and get the noise power half of what we'd get had we used a 1 ohm resistor. (Assuming 1ohm and 2ohm resistors generate equal noise power). Is this already well known besides the fact that n parallel resistors would reduce the tolerance error by n times? Any opinions? Sean 
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when designing regulators balance the amount of current drawn in the error sense circuit with the theoretical noise  i.e. if you have enough current to spare, 1 milliamp drawn by the divider will be less noisy than 100 microvolts  seems simple enough.

Resistor voltage noise En=2*SQRT(k * T * B * R),
k = Bolzman constant T = temperature B = bandwidth of interest R = resistance in ohms Depending on material you also have other noise sources, usually proportional to current. Paralleling n resistors does not reduce noise or tolerance by a factor of n, but by a factor of SQRT(n) because the noise in n resistors is not correlated. If you use that fact and include it in the equation above, you will see that n parallel resistors of X ohms generate exactly the same noise voltage as a resistor of X/n ohms. I would say you have assumed a bit too much about your facts ;) 
Re: Resistor Noises: How to reduce them
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Blasted numbers! :rolleyes: 
Yes, lower resistence means lower noise, whether you use a single resistor or paralleled bunch. But there is some dependency on the type of resistor you use. Wirewound resistors are quieter than the other types.
Take a look here: http://www.aikenamps.com/ResistorNoise.htm To reduce thermal noise, you could try cooling down the circuit with a peltier block or something. But practically, you may have to cool down to liquid nitrogen temperatures to get significant reduction in noise. John. 
Your opinions are much appreciated. I was wrong :o I see now that my assumption that the noise power was independent of the resistance is way too much. I agree with ilimzn:
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Sean :o 
Thanks John.. The web is very informative.
Sean 
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