ZP Delays

[GrindCustoms]

Yo! I'm putting together 2 of Brian's ZP delays, SDX and DD.

BOM asks for BC550, wich variant would be the best to use, A, B or C?

Also, anyone up for doing a little resume about the purpose of those transistors?

Thanks

Rej

[midwayfair]

They're a current mirror.

http://en.wikipedia.org/wiki/Current_mirror#Basic_BJT_current_mirror

You can use literally any NPN there and they'll do their job, but you probably want them to be the same part because the gains will be more closely matched (which is better but hardly necessary for proper operation); and the BC5xx transistors are pretty consistent, which I'm guessing is the reason for the 550 being specified.

[GrindCustoms]

They're a current mirror.

http://en.wikipedia.org/wiki/Current_mirror#Basic_BJT_current_mirror

You can use literally any NPN there and they'll do their job, but you probably want them to be the same part because the gains will be more closely matched (which is better but hardly necessary for proper operation); and the BC5xx transistors are pretty consistent, which I'm guessing is the reason for the 550 being specified.

Cool! Thanks Jon