What type of resistors are low noise resistors? i am using surface
mount (SMD) resistors. I learnt that there are thick film and thin
film resistors. Which types of SMD resistors have lowest noise? kindly
enlighten on this.
Thanks
Kristo
They're all about the same. All resistors have identical Johnson
noise. If there's voltage across them, some may have "excess noise",
which should in theory be very small for metal film resistors. I've
tried to measure the excess noise of various expensive (thin film) and
dirt-cheap (cermet and carbon film) resistors, without success; they
all seem the same.
There is one type of excess noise that's real and measurable:
temperature fluctuations changing resistance in a voltage divider,
converting DC to super-low-frequency noise. That would matter in
instrumantation situations, certainly not audio. We sometimes put
covers over tender circuits to keep air currents off.
Most real-life circuits tend to be dominated by inherent signal noise,
or by the semiconductors, or by bad design.
John