MELF resistors

[gain wire]

Hi, does anyone here know enough as to tell me what the advantages of using melf resistors would be? And are they inductive moreso than regular thick-film or thin-film resistors? That's the only subject of interest that was discussed on the posts on diyaudio. When were they introduced? thank you for your input,
Gain-wire

 

[MarkRehorst]

I don't know about MELFs, but I can tell you a thing or two about MILFs!

(I couldn't let it go...)

I_F

 

[BrianL]

My previous employer forbade MELF because being cylindrical, they tended to roll away from their proper locations if unassembled boards were jiggled too much. These days, there is such a large assortment of "brick"-shaped resistors in various sizes and values that I wouldn't bother about MELFs.

I would imagine that the trimming on MELFs is much like a normal axial-leaded metal film resistor, so there is a spiral trim on it. (my guess is that the origin of MELFs was because they could be made on the same machines as the core of a leaded resistor). However, unless you're up in the high RF or microwave regions, I don't think that the very tiny inductance will hurt you.

 

[gain wire]

So from what I understand they are trimmable? How would one trim them, do you need a laser ? Hey thank you for the info.
O-W

 

[len_scanlan]

I found this link which explains the difference between MELF and the standard surface mount chip resistors. (Note this is a commercial article, plugging the manufacturer's product - not an endorsement from me!)

http://www.sonntag-electronic.de/re...entation/How_to_choose_the_ideal_resistor.pdf

So it looks like the main advantage of MELF is better stability over time and greater surge handling due to the larger surface area of the resistive element


cheers,

Len.

 

[radtech]

MELFs used to be more common than they are now, chip resistors have pretty much replaced them in commercial equipment due to the difference in price, and ease of placement. They're supposed to perform a bit better though.

No, they're not trimmable, he meant trimming during manufacture. I suppose if you were really anal and had your own laser....

I used to build tiny little transmitters with SMT parts, one side of the boards was a ground plane, and I had an idea that with MELFs I could drill a hole through the board and mount the MELF inside the hole, not only saving space, but giving a really good ground connection. Never did get around to trying it, as my usual parts sources stopped carrying them before I got the chance.