Paralleling bipolar transistors

[fjpompeo]

Which is the difference between paralleling bipolar transistors using emitter resistors without base resistors or base resistors without emitter resistors?

I'm designing a psu with 13,8V@25A that will power my HF radio plus charge a 13,8V 45Ah car wet battery, so what configuration should I use?

Positive regulation or negative regulation?

Regards,

Fernando - Call sign PU2PLL - Brazil

 

[flatulent]

The emitter resistor method will force current sharing.

 

[IanP]

As Flatulent stated: " The emitter resistor method will force current sharing ", and will help the transistors share the load more evenly.

You could achieve similar results by using base resistors, but the transistor specifications have to be very closely matched ..
In practice, this would be difficult to achieve unless you have access to quantities of transistors for comparison ..

Below is another example of 13.8V PS with several BJT (emitter resistor configuration) sharing the output current ..

Regards,
IanP