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So much confusion.....
The requirement is a BJT that somehow doesn't get hot while delivering a constant power to a LOAD and using a linear circuit.
The answer is it doesn't exist.
Simple Ohms Law tells us two things:
1. the load has a constant voltage across it and being of fixed resistance must therefore pass constant current.
2. whatever power isn't going into the load is dissipated by the regulator.
The regulator may share the dissipation between a transistor and resistor combination but the power will always be (Power in - Load power) and nothing will change that. The heat sink is there to safely dissipate the regulator power into the atmosphere but it will not reduce the amount disspated, only the temperature it reaches.
So ANY BJT capable of withstanding the voltage across it and the current through it will work and regardless of the actual part number it will produce the same heat.
As this is most likely to involve current amplification rather than voltage amplification (emitter follower configuration) the BJT gain is not particularly important and other parameters even less so.
Brian.
The requirement is a BJT that somehow doesn't get hot while delivering a constant power to a LOAD and using a linear circuit.
The answer is it doesn't exist.
Simple Ohms Law tells us two things:
1. the load has a constant voltage across it and being of fixed resistance must therefore pass constant current.
2. whatever power isn't going into the load is dissipated by the regulator.
The regulator may share the dissipation between a transistor and resistor combination but the power will always be (Power in - Load power) and nothing will change that. The heat sink is there to safely dissipate the regulator power into the atmosphere but it will not reduce the amount disspated, only the temperature it reaches.
So ANY BJT capable of withstanding the voltage across it and the current through it will work and regardless of the actual part number it will produce the same heat.
As this is most likely to involve current amplification rather than voltage amplification (emitter follower configuration) the BJT gain is not particularly important and other parameters even less so.
Brian.