Practical resistor accuracy distribution

Are resistors usually low to save time laser trimming?

Are resistors on the same reel closer than parts from another reel?

The Susumu thinfilms are really good.

The thing to be aware of is that resistor value distributions are often wildly non-Gaussian. The classic example is where there are grades, say 1%, 5%, and 20%. The 5% group will often have a hole that happens to match the 1% distribution perfectly.

A lot of modern resistors are made with a relatively wide distribution, and then machine-sorted into bins. In this case, many of the bins will have uniform distributions. And so on.

Joe Gwinn

I suspect that they may laser trimmed and shipped, not binned.

One batch on a reel could be very close to one another.

Also possible, and maybe a combination of both?

But the fundamental point is that one must measure to be sure, unless one is a large enough customer that the manufacturer will simply tell you.

Joe Gwinn

We just assume that all 1% resistors are within 1%.

We buy 0.1% and some 0.05% parts too. Since most of our products have software-based calibration, we mostly care about resistor tempcos, not so much tolerances.

Yes, and calibration will wash all those strange-distribution woes away.

Joe Gwinn

One could cal out tempcos, but test time would be outrageous.

We are bidding on one unit that might need that. Yuk. The alternative is to, basically, ovenize the PCB.

Top-end crystal oscillators have been relying on that for decades now.

Peltier junctions let you stabilise the board temperature close to room temperature, which can reduce long term drift.