I have been trying to assemble a simple 5V regulator circuit using the L7805CV and have had no luck at all getting the output to 5V. I have tried many circuits and multiple L7805CV regulators, thinking that maybe it was the regulator itself that wasn't doing its job.
So far the closest I've come to 5V is 6V, which won't work for what I'm trying to power.
First, I tried the simple circuit with a 10uF cap from input to ground pin and 1uF cap from ground pin to output, and was getting 3.8V output with an input of 9V. I was getting 11V out with a 12V input.
I tried another one that was similar but with a 1K resistor connected to an LED on the output, which gave me 6V. I thought maybe the capacitors were the cause so I tried going with 100uF from input to ground and a 10uF from ground to output and another 100nF on the output for filtering and still no luck. I basically played with cap values all the way up to 2200uF and didn't get anything close to what I needed. I either got really low (about 3V) or really high (close to 12V) on the output and also tried different input values of 6V, 9V, 12V, and even 18V and nothing worked.
I used a heat-sink on the l7805CV and am stumped how this is happening. I eventually went back to one of the first designs that had the output of 6V and tried using a diode on the output for its voltage drop and was getting almost the exact reading on the output (actually a few mV higher) and am stumped at this point. After a while I got bored and tried out a few different transistors I had around to see how they would affect the circuit and was surprised to find almost exact results.
What am I doing wrong? How can I successfully achieve 5V on my output?