[Milsurplus] CarbonFilm / Metal Film Resistors

[J. Forster]

I'm not sure there is really one answer to this question.

The issue is the inductance of the film and that depends on the number of 'turns' the film makes. Any value can be made without any turns of a high resistivity material (high ohms/square) or made up of several to many turns of a low resstivity material. It is possible, even likely, that two apparently identical resistors from the same maker may
have different Ls. Many resistors have their values determined by automatically cutting spirals in the resistive film with a laser or abrasive jet.

The only ways I can think of it to check the Rs you actually plan to use or look at the spec for a 'Worst Case' L value.

At a guess, if you are talking about 1/4 or 1/2 watt resistors, of 47 ohms or more, I'd ignore the issue for frequencies less than 10 MHz, BUT THAT's JUST A GUESS.

FWIW,
-John


jimandterri at bellsouth.net wrote:

> When replacing carbon composition resistors, at  what frequencies do I need to be concerned about the inductive effects of the newer carbon film and metal film resistors, I assume the metal film would be far more of an issue  I have seen some vague suggestions but not much specific info. Has anyone seen any real world problems in this area?
> JMS.