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RE: Metallic oxide resistor ok sounding in the feedback position?

Posted by TimFox (A) on August 21, 2015 at 11:46:49

In Reply to: Metallic oxide resistor ok sounding in the feedback position? posted by DAK on August 14, 2015 at 01:38:42:

The physical effect alluded to in the other posts is voltage co-efficient of resistance, which can be large in high-voltage applications. It is a rare resistor that has a real specification of VCR from its manufacturer. At the physical level, VCR is governed by the material and the voltage gradient (V/mm) along the element. Therefore, small resistor packages (especially SMT) with bad materials suffer from this non-linearity. Metal film, metal foil, and wirewound metal alloy resistors are the best materials. I have had real, measurable problems with this VCR in critical analog applications with 0805 and 1206 package SMT resistors at only 10 V across the resistor. It is not easy to measure this with home-lab-quality equipment, but I have had success building an old-fashioned Wheatstone bridge with General Radio resistor boxes (wire-wound).

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