I'm trying to decipher the diagram on page two of the datasheet:
http://www.mouser.com/ds/2/389/tip102-957196.pdf

So the Y axis is 0 amps, 1 amps, 10 amps, 100 amps, and the X axis is 0 volts, 1 volt, 10 volts, 100 volts correct?
Can I just look up 1 amp and 10 volt, and observe that its under the "DC operation" curve and assume that I will not need a heat sink?

 

Would you mind being more specific please? In my original post, I was looking for an explanation on why the transistor and how this is not just on/off. I was also asking what specific transistor. Did you take a look at either of the 2x circuits I posted?

Pick a complementary pair of transistors as if you were building an audio amplifier - we can't keep comprehensive selection guides in our heads, I'd suggest picking transistors in the TO126 package style.

You can build it like an audio output, but the bias diodes are less than convenient with an op-amp driving it. If your op-amp is fast enough - you can dispense with the bias diodes and emitter resistors. Include the transistors inside the nfb loop and the op-amp will do its best to smooth out the crossover distortion.

 

Pick a complementary pair of transistors as if you were building an audio amplifier - we can't keep comprehensive selection guides in our heads, I'd suggest picking transistors in the TO126 package style.

You can build it like an audio output, but the bias diodes are less than convenient with an op-amp driving it. If your op-amp is fast enough - you can dispense with the bias diodes and emitter resistors. Include the transistors inside the nfb loop and the op-amp will do its best to smooth out the crossover distortion.

Hi Ian, this circuit has already been completed and working a while ago. I was asking about how to calculate power dissipation in this darlington transistor.

 

Does my reasoning in #41 seem to make sense? Can I assume I don't need a heatsink for this transistor? Can someone please validate this?