Hi guys,
I've been looking over the typical applications in the datasheet for various 78XX voltage regulators trying to build and learn more about each configuration when I came across the two designs for high current and high current with short circuit protection.
My confusion arises because of the use of PNP transitors and the term "B" in the formulas for determining both
R1 and Io in the high current configuration.
I understand that the PNP's function is to pass the higher current. What I don't understand is what role R1 has in biasing the transistor. From what I can see there is no base resistor resulting in a high emitter/base current. How does this not blow the transistor?
For the short circuit protection, what is the logic in providing short circuit protection based on the transistor configuration?
I've been trying to study PNP basics but can't seem to wrap my head around them. NPNs haven't been too much of a problem.
Thanks,
Dave
I've been looking over the typical applications in the datasheet for various 78XX voltage regulators trying to build and learn more about each configuration when I came across the two designs for high current and high current with short circuit protection.
My confusion arises because of the use of PNP transitors and the term "B" in the formulas for determining both
R1 and Io in the high current configuration.
I understand that the PNP's function is to pass the higher current. What I don't understand is what role R1 has in biasing the transistor. From what I can see there is no base resistor resulting in a high emitter/base current. How does this not blow the transistor?
For the short circuit protection, what is the logic in providing short circuit protection based on the transistor configuration?
I've been trying to study PNP basics but can't seem to wrap my head around them. NPNs haven't been too much of a problem.
Thanks,
Dave
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