Does one really need TO-126 to drive darlingtons at “low power”?
Small signal transistors would likely perform better. If you’re bent on TO-126’s there probably isn’t any better choice than the BD139/40 - which are almost identical to Toshiba’s TTA/C008. Either needs to be biased up to at least 5-10 mA to get the fT out of the dirt. Unless of course the 60 volt versions are high enough. At “low power” the low voltage parts are better because their hFE holds up better at low Vce. Those last 2-5 volts of swing are more critical with 30 volt power supplies than with 80 available. Thats where high voltage transistors tend to fall apart, gain and bandwidth-wise.
Small signal transistors would likely perform better. If you’re bent on TO-126’s there probably isn’t any better choice than the BD139/40 - which are almost identical to Toshiba’s TTA/C008. Either needs to be biased up to at least 5-10 mA to get the fT out of the dirt. Unless of course the 60 volt versions are high enough. At “low power” the low voltage parts are better because their hFE holds up better at low Vce. Those last 2-5 volts of swing are more critical with 30 volt power supplies than with 80 available. Thats where high voltage transistors tend to fall apart, gain and bandwidth-wise.
Last edited:
