Tantalum Capacitors, what I've learned

[jebem]

(05-09-2021 07:14 PM)AndiGer Wrote:  I have a capacitor tester that also gives ESR as a result. But: what is high or what is low ESR?
Didn't find a realistic answer ...

No definitive answers, agreed.
The lower ESR, the better.
But ESR value depends on the reading equipment quality. Most units use a fixed frequency for testing, but from a practical point of view, we compare ESR for fresh production batches of new caps for each capacitance value and working voltage and select the best ones for our application.
So there is no absolute reference as I see it.
But the same is valid for the capacitance real value. A lot of say, 10 caps of 100uF nominal value may present deviations like +50% on some of them, and usually the value will be at least 10% higher.
Many vendors used to care and published charts in the good old days.
ESR impact would depend on the circuit design and application type of course.

For small electrolytic cap values, a low ESR would be a value below 0.5 ohm.
Again, it all depend on the circuit requirements.