2n3055 Transistor

[jisoo]

The transistor 2N3055 is packaged in a TO3 case. It has its collector "grounded" to the case, and the base and emitter to the two pins. NPN transistors are usually used with the emitter going directly to the ground, and the collector somewhere far from the ground. Can someone give me a typical application for this 2n3055 transistor, showing how it is typically used in a circuit? What am I missing? The MJ2955, it's mating PNP, is the same way, and this, in a PNP makes sense. Thanks for your help.

 

[IndianEars]

The 2N3055 was the mainstay of audio amplifier power transistors for over a decade or 2, since it was launched. It is still available, but other better (More power, better frequency Response) have now displaced its pole position.

The 2N3055 is available in TO-3 casing as well as TO220. The TO3 casing is the largest and provides the best heat dissipation, when connected to an adequate Heat sink.

The 2N3055 in TO3 is rated for upto 115 Watts power dissipation.

The 2N3055 is a Power Transistor, ie its characteristics are optimised for delivering High Power. However, generally, it is the same as ANY Other transistor.

ALL Transistors when operated linearly (for analog signals - Non Switching applications) will ALWAYS have:

• The Base-Emitter Junction Forward Biased (0.7 Volts)
• The Base-Collector junction reverse biased. (Almost All the voltage across the transistor)

Hence the Collector-Base Junction dissipates practically ALL the power (Power = Voltage x Current and Current thru the collector & Emitter are almost identical)

Hence the Collector junction is connected to the Body of the transistor, so that it can be connected to a Heat sink to keep it cool.

Look at the Circuit Diagram of ANY Audio power amp using 2N3055 Power Transistors and you will see how its used.

The JLH 10 Watt Class A Power Amplifier is a Good example.



Also look at Non Class A audio Power Amp Circuits like this one.




Cheers