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I'm looking for a diode with a forward voltage (VF) of 0.6 V at 10 mA IF.

While searching for it, I came across many diodes' datasheets where they seem to contradict themselves.

For example: BAV99

Enter image description here

Enter image description here

As in the table, it says VF is 0.855 V at 10 mA IF at 25 °C, while in Fig 1 it is around 0.75 V.

For this one, it is just 100 mV difference, but I've seen other diodes with a higher difference.

Which part of the datasheet should I use?

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3 Answers 3

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I'm afraid the datasheet is correct.

It's all about typical and maximum ( or sometimes minimum) parameters.

The table you point out is the maximum Vf for some given condition, i.e. it tells us that any specim of such a diode is guaranteed not to exceed that value. This is to allow for manufacturing tolerances.

The graph below instead depicts the behaviour of one typical diode in varying conditions.

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Most important part you've missed, that the table states maximum (guaranteed) values for the conditions. While the graph on the Fig. 1 shows you some sort of typical values. Which are basically averages between different diodes & batches. These parameters may vary slightly from one batch to another or even within the same batch due to manufacturing imperfections.

Answering your last question "which part of datasheet to use?", mostly you do your calculations for either the worst case scenario or the best operating conditions. So most likely you should pick maximum values here. That's why they write these on the table as usually only these numbers will matter.

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To vastly oversimplify the design process, you use extreme specs like maximum when analyzing whether your design will meet your design requirements. You use typical specs when analyzing how close you are likely to come to your design goals.

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