Marc, There's nothing that sez that if you have two txstors that match at 1mA DC that they'll match (even closely) at 2 amps. hfe is nonlinear with respect to just about all parameters: Vce, temperature, I, etc.
Can you build a test rig and measure parts at the actual currents, temps, and voltages you'll be using in your final ckt? Also, depending on how close a match you want to get, you may need a good number of parts to choose from ($$$). If you can get away with sacrificing some current, you can ballast the txstors with emitter resistors, to make some of the mismatching go away. Phil Marc Price <[EMAIL PROTECTED]> wrote: > Seen as the Tesla coil mailing list is down i thought i might ask this > question here > > i tested 2 x 2n3055 transistors and i read that you need to match the 2 > but what > i dont know is, do i need to have them exact or just close. > > transistor 1 gain Hfe = 123 > transistor 2 gain Hfe = 194 > > Any ideas > > Marc :-P >
