What should I look for ?
What makes a BJT with high Early voltage ?
What kind of BJTs have high Early voltage ?
What makes a BJT with high Early voltage ?
What kind of BJTs have high Early voltage ?
For a given process, there is an inverse correlation between Hfe and Vaf (e.g. a BC548A will normally have a higher Vaf than BC548C), but other than that, I do not see how you could infer Vaf from modern datasheets; ~50 years ago, manufacturers provided detailed parameters like Hoe, which could give you a lead, but that's no longer the case.
Do not think that opting for a low Hfe type will ipso facto provide a high Vaf: power HV transistors have a low Hfe, AND a ridiculous Vaf.
Also, do not rely on historic datasheets: a modern 2N2222 (or its SMD version) has a much higher Vaf than one made in the sixties
May be there are some processes giving high VAF ?
VAF is the name for the Early voltage in LTSpice models.
Datasheets do not give VAF, can we trust Spice models ?
I could poke in model libraries to look for high VAF( and BF ) like this library For LTspice users. Libraries of models, examples, etc
There are certainly processes yielding a high Vaf, but only the manufacturer has that knowledge.
Vaf has never been explicitly published, even when datasheets comprised 10+ pages.
What historic datasheets included is Hoe (BC107-109 for example), which allows you to compute Vaf, but as I said, this kind of detail is never mentioned presently, and old data is not applicable to modern devices, even if they carry the same type number
Vaf has never been explicitly published, even when datasheets comprised 10+ pages.
What historic datasheets included is Hoe (BC107-109 for example), which allows you to compute Vaf, but as I said, this kind of detail is never mentioned presently, and old data is not applicable to modern devices, even if they carry the same type number