David wrote:
what doping is used for PNP RF transistors and saturated switches if it is not gold? Does it also increase leakage?
I replied:
Gold doping doesn't affect the speed of BJTs in the active region very much -- its purpose is to reduce minority carrier lifetime and, thereby, to reduce storage time when a transistor recovers from saturation. I'm not sure how manufacturers deal with this in the case of PNPs.
After I posted, I recalled learning in a long-ago device physics course that both Gold and Platinum doping were used to reduce minority carrier lifetime in PNP saturated switches. According to Motorola, the MPS3639/3640, 2N4209, and 2N5771 were gold-doped PNP saturated switches (all are now obsolete, although SMD versions of the 3640 and 5771 appear to still be available).
And yes, doping PNPs with either Gold or Platinum does increase reverse leakage current (Platinum less so than Gold).
Best regards, Charles _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
