voltage regulators

[Kevin Weddle]

I was working with independent power souces when I discovered that the book example of a voltage regulator falls short. It appears that a single pass transistor is not adequate if the regulator is to sink current. You must have a complementary transistor. Can anyone corroborate this?

[audioguru]

I discovered that the book example of a voltage regulator falls short. It appears that a single pass transistor is not adequate if the regulator is to sink current. You must have a complementary transistor. Can anyone corroborate this?

Horray! Kevin's back. ;D

Hi Kevin.
A series pass regulator sources a voltage to a load. The load sinks current to ground.
A shunt regulator like a zener diode sinks excess current to ground all the time from a series source resistor and the shunt regulator is parallel to the load.

Maybe you are thinking of a circuit that is powered by a series regulator that has an inductive part that applies its flyback voltage to the output of the regulator. Then maybe the inductive part should have something to sink its voltage to ground.

[Kevin Weddle]

Thanks Audioguru. I really enjoy your articles. In this post, I was taking a positive 5 volt regulator and applying that to a positive 18 volt regulator through a resistor. A simple NPN pass transistor, in this case, can't operate. But if you add the other complimentary transistor, then the positive 5 current adds with the positive 18 current through that transistor.

[audioguru]

I don't know how or why you are trying to add the current of a 5V regulator with the current of an 18V regulator. Surely then the combined output isn't regulated.

If you need an 18V regulator with higher output current then use a regulator or booster transistor with it that will handle higher current.