Resistor noise notes
Posted: Sun Jul 24, 2011 11:44 am
As found here. viewtopic.php?f=58&t=1218&start=146
The high lights, a 5% resistor can be obtained with specific technologies. 1% resistors costs about the same and use a different technology. The % spec isn't just the long term resistor ratting, but also the short term. Variations will happen as you pump in an AC signal, which will cause a wave of heat across the chip. This wave of heat will cause a wave of thermal expansion, which will cause the resistor to wonder in the 5% range. In an amplifier design(s), this can cause noticeable acoustic noise when driving a speaker. So might as well use the 1% resistors, as they cost nearly the same, and are better.
Here's a copy of Fred's post,
The high lights, a 5% resistor can be obtained with specific technologies. 1% resistors costs about the same and use a different technology. The % spec isn't just the long term resistor ratting, but also the short term. Variations will happen as you pump in an AC signal, which will cause a wave of heat across the chip. This wave of heat will cause a wave of thermal expansion, which will cause the resistor to wonder in the 5% range. In an amplifier design(s), this can cause noticeable acoustic noise when driving a speaker. So might as well use the 1% resistors, as they cost nearly the same, and are better.
Here's a copy of Fred's post,
Vishay application note: http://www.c-c-i.com/sites/default/files/vse-an00.pdf
"Carbon composition resistors can exhibit a noise index of 0 dB while bulk metal foil resistors may have a noise index of -40 dB, usually making the excess noise of metal foil resistors insignificant."
http://en.wikipedia.org/wiki/Resistor#E ... rmal_noise
Yes, I realise that it's not really applicable to engine management, but you may as well have the best where you can have them with no downsides including no excess cost
