I am using an LM317T, trying to use it to create a constant 5v output. I've wired it from the diagram shown here. I am using a pot trimmer to control R2. As far as I can tell, it's wired properly (checked a few times).
What's happening is; if the input voltage is above 5v, it will limit the voltage to 5 volts. But if the input voltage goes below 5v, so does the limit voltage. It seems that it is creating a cap instead of a constant. It's capping the voltage to 5v, but when I go below 5v, it mirrors whatever the voltage is.
Is there a common mistake that I might be making? I've made this circuit before with success, but I think I was using an LM317 instead of the LM317T. Would this make a difference?
Best Answer
It's a linear regulator. It can only decrease voltage, cap it, as you've said. It is working appropriately as you've described it.
If you want to be able to go up or down from the input voltage you need a buck/boost topology.