[G0HZU_JMR]

Hi John

Sadly, I'm not really an expert on this stuff, but if you go back 40 or 50 years then there were quite a few JFET manufacturing processes that were established across the industry. The same applies to BJT transistors. I think this allows a manufacturer to make a process 50 JFET from an agreed JFET process recipe book.

The two images below are from an old Nat Semi databook. The first one shows all the devices they make using process 50.

The well-known 2N3819, MPF102, BF245, BF256 and 2N4416(A) are included here and the parts with an asterisk are the preferred parts. You can see an image of the internal die.

The second image shows process 92. The common process 92 JFETs are the U309, J309, U310 and J310

You can see the die is very different between the two processes. In the past I've compared the die for process 50 across several manufacturers and the die pattern can differ slightly in terms of the shape and the number of interlocking fingers. So, I'm not sure what the rules are for each process.

I'm not sure why there are so many part numbers within process 50, but some of it can be explained in terms of device packaging and pinout differences. Inside the process should be the same.

I guess in the case of the 2N5484, 2N5485 and 2N5486 the parts get assigned a part number depending on where they fall within the accepted range of process 50. One batch might all end up as 2N5484 for example. However, I'm really just guessing. Maybe someone else can describe it all better.