Regulating voltage

[parish.60]

This may be a simple question, but I was wondering if anyone could help me figure out how to take a 5 volt input and regulate it down to about 4 volts. If at all possible it would be great if this were in some way adjustable so i could have a voltage output range of 0 to 5 volts.

Thanks

 

[magvitron]

try a zener diode in series

 

[picbits]

You've not said how much current you need, what level of regulation you need and what kind of environment it's in.

 

[ronsimpson]

Most regulators do not work well with no or little voltage across them. 5Vin 4.5V out. The are low drop out regulators but a standard regulator needs 1 to 1.5V across it.

Most adjustable regulators do not work well with output voltages below 1.5 volts. If going to 0 volts is important then that can be done it you have to have it.

Low dropout voltage and adjustable to o volts is double hard.

Please, what are you trying to do? Where is the 5V coming from?