alternative low Vce(sat) transistor for smaller heatsink

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Hello,

I have a shunt DC power supply that outputs about 3 amps and I am using some older FJPF5200 NPN transistors:

https://www.mouser.com/datasheet/2/149/fjpf5200-298548.pdf

I am needing to connect the FJPF5200 to a pretty good sized heatsink.

I have been looking at Low Vce(sat) Transistors:

ON Semiconductor

These parts have a Vce(sat) that is way less than the FJPF5200.

So, these should have a lot less heat output and I could use a smaller heat sink or possibly none at all.

Has anyone had any experience with these low Vce(sat) parts for audio?

Any suggestions ?
 
Low saturation voltage is great if you're using the transistor as a switch. From what info you've given sounds like you're using the transistor in a shunt regulator - that's a linear application and the Vce(sat) spec won't help you save heat there. To save heat you'd need to use a switching reg.
 
Low Vce(sat) devices have to have low emitter-spreading resistance, and often are very low noise as a consequence. The ZTX851 family being a well known example.


Low Vce(sat) normally implies low Vbe at high currents too, again due to the low emitter-spreading resistance.


For an analog emitter follower the parameter usually of interest is how well the gain holds up at high current (ancient devices like the 2N3055 completely fail to do this!). Low Vbe at high currents is good too of course as less headroom is needed.
 
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