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Let's say we have vanilla BC846 (80V), BC847 (50V), BC848 (30V) transistors from the same company, each with 3 bins A, B, C where C supposed to have to highest hfe.

Is that correct, that BC846C should be the fastest, and for example BC847C or BC846B are slower (i.e. have higher capacitances and slower switch-on/off speed)?

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I would think they're equally fast, since the datasheet mentions just one value for \$f_T\$, not different values per \$h_{FE}\$ class.

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  • \$\begingroup\$ Yes, that's official information. But in reality they should be different - lower max. voltage and higher hfe should mean thinner base => higher speed. \$\endgroup\$ – BarsMonster Jun 24 '11 at 10:08
  • \$\begingroup\$ @BarsMonster, Or they could be adding dopant which has a small change in leakage current and causing the channel to have a higher mobility. There is no way to just look at two transistors and know based off of voltage rating. \$\endgroup\$ – Kortuk Jun 24 '11 at 10:37
  • \$\begingroup\$ I an impression, that pins appears from the fact that parameters have some variation, and transistors are just sorted by the results of actual tests... \$\endgroup\$ – BarsMonster Jun 24 '11 at 12:29
  • \$\begingroup\$ @BarsMonster: for \$H_{FE}\$ very likely, for \$V_{CE}\$ I don't know. How would you test this non-destructively? \$\endgroup\$ – Federico Russo Jun 24 '11 at 12:38
  • \$\begingroup\$ Vce brakedown is not destructive when you do so with controlled current (i.e. 1-10ma max). \$\endgroup\$ – BarsMonster Jun 24 '11 at 12:40

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