Thin Film Resistor Rated Power and Voltage: 24,431 of 93,914 Walsin Rows Imply Over 100 V, and the Export Has No Voltage Column

Thin film resistor rated power and voltage are tied by one line of arithmetic, and Walsin’s export publishes only one side of it. We computed the voltage each of 93,914 rows would need to dissipate its rated power. 24,431 rows (26.0%) imply more than 100 V, 606 imply more than 1,000 V, and the peak is 1,732 V.

A rated power only tells you what a resistor can dissipate if it can survive the voltage that dissipation requires. Venatech Limited, an authorised Walsin distributor in Hong Kong, holds all 203 parametric export files published by Walsin Technology (Walsin). This post is measured from the Rated Power and Resistance columns of the eleven non-empty thin film files, 93,914 rows, and every part number below is real. The arithmetic is ours, not Walsin’s. We do not hold a thin film datasheet, so the real maximum working voltage of every part here is a number we cannot give you.

Why does a thin film resistor’s rated power imply a voltage?

Because power, voltage and resistance are one equation. A resistor dissipating P watts at R ohms sees a voltage of the square root of P times R across it. For WF25Q3004TTL, a 3 megohm, 1 W part at 2512, that figure is 1,732 V. If the part’s own voltage limit is lower, the rated power is unreachable at that resistance, and the wattage column overstates what the part can do.

We call this figure the implied voltage. It is not a rating and it is not a limit. It is the voltage at which the wattage printed in the export would become true. Our post on high voltage chip resistors covers the thick film case, where Walsin’s datasheet takes the lower of the power-derived voltage and a size ceiling. For thin film we hold no such sheet, so the implied voltage is the only voltage the data supports.

How many Walsin thin film rows imply more than 100 V?

24,431 of 93,914, and it rises with every footprint. We computed the implied voltage for all 93,914 rows and counted them against four thresholds that we chose, not Walsin. Above 100 V: 24,431 rows (26.0%). Above 200 V: 15,019 (16.0%). Above 500 V: 4,646 (4.9%). Above 1,000 V: 606 (0.6%). The median row implies 21.9 V, so the long tail is a small share of the catalogue and a large share of the high-resistance end.

We have not seen this counted anywhere. The 1210 footprint tops out at 998.0 V, two volts short of 1,000. Every row above 1,000 V is at 2010 (408 rows) or 2512 (198 rows). No thin film row at 0201, 0402, 0603, 0805, 1206 or 1210 reaches it.

What does the voltage ladder look like from 0201 to 2512?

Steep at the bottom and flat at the top. We took the largest implied voltage at each of the eight footprints and divided each by the one below it. The steps are 7.14, 1.98, 1.58, 1.58, 1.26, 1.50 and 1.15 times, so 0201 to 0402 multiplies the ceiling seven-fold and 2010 to 2512 adds only 15%. The jump at the bottom is not about power. It is because 0201 stops at 12 kilohm, which caps the product P times R.

The “power at 100 V” column is pure Ohm’s law: 100 squared over the resistance, set against the rated power. At 100 V across 3 megohm, a 1 W part dissipates 3.3 mW. The wattage that matters to your thermal budget at that value is a few milliwatts, and the footprint’s rating tells you nothing about it.

At what resistance does rated power stop being reachable?

At a value that depends only on the voltage you feed it. The crossover resistance is the voltage squared divided by the rated power. At 100 V, the crossover is 200 kilohm for a 1/20 W part, 100 kilohm for 1/10 W, 25 kilohm for 2/5 W and 10 kilohm for 1 W. Above it, a circuit at that voltage cannot make the part dissipate its rating.

Read the last row twice. At 2512, 457 of the 1,181 distinct resistance values sit above the 100 V crossover, so in a 100 V circuit more than a third of the resistance range cannot reach the 1 W on the label. In a hypothetical 200 V circuit the same applies to every value above 40 kilohm. These are illustrations of the equation, not Walsin limits.

Does the series change the picture?

Yes, because the series differ in resistance range and wattage. The share of rows above 100 V is 20.7% for the WF precision series, 32.5% for MF tantalum nitride and 37.9% for SF anti-sulfuration. The WF line owns the single highest figure, 1,732 V. The MF line stops at 1 megohm and peaks at 632 V.

MF is one cell: 1206 at 2/5 W, all 20,520 rows. SF is almost all 2010 (14,810 of 15,080 rows). Compare the wattage ladders in thin film resistor power rating by case size.

What does the Walsin export say about the voltage limit?

Nothing. We opened all eleven non-empty thin film files and read every column header. The schema has nine columns and none of them is a voltage: Part Number, Series, Size, Resistance, Tolerance, TCR, Rated Power, Packaging, Termination. There is no maximum working voltage, no overload voltage and no isolation voltage on any of the 93,914 rows. Two of the nine, Packaging and Termination, hold one value on every row.

So an engineer who filters on 1 W at 2512 and 3 megohm gets a part number, and the file gives no way to learn that the part may be limited by voltage to a fraction of that. A cross tool that matches on size, resistance, tolerance, TCR and power can return a pair that agrees on every published field and still differs on the one that a high-resistance circuit depends on. That is why our cross reference states differences and does not tick a box.

What should a buyer do before trusting the wattage?

Four steps, and the first is one line of arithmetic that already separates the 69,483 rows implying 100 V or less from the 24,431 that do not. Take them in this order.

1. Compute the implied voltage for your own part. Take the square root of rated power times resistance. If it is below your circuit’s working voltage, power is the binding limit and the wattage is meaningful.
2. If it is above, ask for the voltage limit. Request Walsin’s specification for the exact part number. We hold 28 Walsin datasheets, 451 pages, and none covers thin film, so the number has to come from Walsin’s published specification.
3. Compare like with like. Your incumbent’s voltage limit goes in the blank column above. A match on wattage is not a match on voltage.
4. Do not infer a limit from the footprint. The ladder above shows the implied voltage rising from 22.4 V to 1,732 V across eight sizes, which is arithmetic, not a specification.

What is in Hong Kong is on ready stock, a dated snapshot of 1,125 part numbers as at 23 September 2026. For the line itself see thin film.

The short version

A thin film resistor’s rated power implies a voltage, and Walsin’s export publishes only the power. 24,431 of 93,914 rows imply more than 100 V, 15,019 more than 200 V, 4,646 more than 500 V, and 606 more than 1,000 V, all of them at 2010 or 2512. The ceiling climbs 22.4, 159.7, 316.2, 500.0, 789.0, 998.0, 1,500.0 and 1,732.1 V from 0201 to 2512. At 100 V, WF25Q3004TTL dissipates 3.3 mW of its 1 W. The export has no voltage column on any row, and we hold no thin film datasheet. Compute the implied voltage for your part, then ask Walsin for the limit. Qualification stays with you.

Send us the part number, resistance and working voltage from your drawing and we will say which side of the crossover it sits on. And a question back: when you derated a 3 megohm resistor by its wattage, which limit did you think you were protecting?

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