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I'm having trouble finding what I want due to the way mouser.com limits searching on BJTs. I'm trying to find out if anyone manufacturers a medium to high power BJT with a gain of at least 30. The higher the better. The classic 2n3055 has a minimum gain of 20. I want something higher if possible. Does anyone know if there's anything out there with such high gain and also moderately high current capability?

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  • \$\begingroup\$ You'll have to be a lot more specific than that. What Vceo do you need? How many amps? Watts? But if you want a better 2N3055 you could look at MJ15003 and 2N3773 for a start. The latter has a very consistent gain of around 140, I've measured it over many samples. \$\endgroup\$ – user207421 May 25 '13 at 23:56
  • \$\begingroup\$ I was intentionally vague because I wanted some folks to just throw out some stuff for me to look at. I have no idea what practical ranges are. I'm extremely flexible on the Vceo and the collector current and watts. I'm willing to go up or down from the kinds of characteristics you get on a 2n3055. I'm just trying to find out what's reasonable if I want something with say 40 or 50 or even 100 minimum Hfe. I see a lot of extremely lower power signal transistors with that kind of value. But I want something for actual output power. \$\endgroup\$ – JamesHoux May 26 '13 at 0:14
  • \$\begingroup\$ EJP: Ok I'm baffled. I just looked up the 2n3773 you recommended. It says it has a minimum Hfe of only 15. You're saying it has 140??? \$\endgroup\$ – JamesHoux May 26 '13 at 0:20
  • \$\begingroup\$ I tested a box of 25 and they were all within Hfe=138-145. \$\endgroup\$ – user207421 May 26 '13 at 1:03
  • \$\begingroup\$ @EJP, at what collector current? From the On Semi datasheet you shouldn't expect the same beta at 16 A as at 1 A. \$\endgroup\$ – The Photon May 26 '13 at 3:03
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The Motorola MRF454 is an RF power transistor. The datasheet says it is intended for operation up to 30 MHz, calls out minimum hFE of 40, and says the device is rated for 80 watts power out.

This is probably not what you want if you are looking for a high-gain 2N3055, as the 2N3055 is intended for DC operation. It is a linear power supply pass transistor.

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This question was a poor question... formed from misinformation I read on another electronics site. Recommendation was to always use minimum Hfe in doing calculations. When I look at transistor curves on datasheets, it appears that the recommendation is misleading.

Maximum Hfe occurs in a range of low base current. At a certain 'grey area', as base current further increases, collector current doesn't increase as much. That means the minimum Hfe is only a factor when trying to drive a transistor full on. It's also somewhat of a conundrum since a BJT is never technically 'full on' (as you'd get with a FET). The Hfe simply gives diminishing returns that approach zero once you are pushing enough base current. Since you get diminishing returns, it's not quite realistic to just pick a certain value to turn the transistor full on and then aim for it.

I'm less concerned with minimum Hfe now -- as it's only a rough guide in power transistors.

This comes out of me having had a lot more experience with FETs than BJTs, so I didn't quite have a proper view of things.

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    \$\begingroup\$ Generally, you should design to the datasheet minimum or maximums. The "typical" values and characteristic curves are informative only and there's not guarantee from the supplier that parts delivered will meet anything except the actual mins and maxes. But for short runs or hobby work its not uncommon to use typicals but if you're smart you'll test your parts before using them to make sure they are meeting the requirements for your circuit. \$\endgroup\$ – The Photon May 26 '13 at 2:56
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    \$\begingroup\$ That said, On Semi offers NSS12601CF8 with min beta of 200 and 6 A I_c. \$\endgroup\$ – The Photon May 26 '13 at 3:00

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