MJ15015's are better but about 3x the cost. Personally I don't think running the junction at the maximum temp is a good idea so you need to allow some margin - 20-30W is perhaps on the low side but it's definitely a challenge to get more than 40-50W per 2N3055 and keep the junction below 150-170 oC. With an ambient temp of 25 oC that translates to 60W even with a substantial heatsink. The max junction temperature is 200 oC - 115*1.52 is 174.8 so if the device is dissipating that much power the case can be at no more than 200-174.8 or 25.2 oC If you add in the typical resistance of a mica washer of 1 oC/W and maybe an 0.5 oC/W heatsink (i.e fairly meaty) then there's going to be around 3 oC/W junction-to-ambiant resistance. 3.3.1, which shows the basic doping of a junction transistor and Fig. The difficulty comes from the junction-to-case thermal resistance which, for the 2N3055, is 1.52 oC/W. The way a transistor works can be described with reference to Fig. It was one of the first silicon power transistors, offered unrivalled second breakdown immunity and found many applications particularly in audio power amplifiers. Features DC Current Gain hFE 20 70 IC 4 Adc Collector Emitter Saturation Voltage VCE(sat) 1. The 2N3055 power transistor was introduced by the Radio Corporation of America (RCA) in the early 1960s. Yes - in fact this surprises people who see the 115W rating and assume that's what the transistor can handle forgetting that the 115W is at a case temperature of 25 oC. 2N3055/D 2N3055(NPN), MJ2955(PNP) Preferred Device Complementary Silicon Power Transistors Complementary silicon power transistors are designed for general purpose switching and amplifier applications.
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