Beta matching for multi-coil/filer builds

[Nofear]

sorry guys....

third time the charm!??
transistor matching.pdf

[min2oly]

And here's the million dollar question:
- If we are using the transistors for switching why is it important to match them based on their Hfe? In my mind that is a static snapshot.
- Shouldn't we be more concern about their dynamic behavior?. i.e how fast do they open, how fast do they close. How abruptly are they closing? (leakage current etc)

This has been my question all along, well put. It is why I attempt to match them under the circumstances they will actually be used.

You did some good work there. I'm open to any ideas you might have to better measure the dynamic behavior as you put it - very nice.

Another method I've used to double check if transistors are matched is to monitor their temperature. Push the energizer hard then measure, back off then measure, tune where you like it then measure - If one transistor is getting much hotter than the others, it has to go :-)
Thanks for sharing your work, it really helps to see others going through the process.
Kind Regards,
Patrick

[Tom C]

you want 12 volts to the base no less..... has to work in its soa for the device.

Tom C