Electronic – NPN vs PNP current limiter


So I'm trying to design two mirroring current limiters for a +-15 volt power supplies.

I don't understand why these two circuits don't behave more like each other.
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The PNP circuit has +15 on the top and ground on the bottom and

The NPN has ground on top and -15 at the bottom.

The npn limits at around 600mA which is what we expect ,but I'm not sure why the PNP is 450mA.

I don't understand why the Vbe on the PNP is only 0.46 V and not around 0.65.

Any comments are much appreciated.

Best Answer

Looking at the datasheet, we can get the current gain for both PNP and NPN:

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It seems that the NPN variant gives sightly higher current gain than the PNP variant. There are more parameters that differ, probably the VBE, etc. which is a reason why both configurations won't give same results.

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