I am using the L78L33 (http://www.st.com/stonline/books... ) to produce a 3.3V output, wired up as shown in the attached image. My Vin = 5V basically from my computer's USB port.
Here is what I observed:
1. Cin = 0.1uF or Cin = 0.30uF (since I don't have a 0.33uF) cap and Cout = 0.1uF, I get Vout = 3.78V. This is on the breadboard.
I think I can solve this to Vout = 3.38V with a rectifier diode of 0.40V drop in series with the Vout.
(Same results if I used ceramic or multi-layered ceramic caps.)
2. Here is what puzzles me (and without a rectifier diode) I actually created a breakout board with both Cin = Cout = 0.1uF using the multi-layered ceramic caps. I get consistently 4.33V--very stable. Again my Vin is 5V but with a polarized 100uF of 16V in parallel to the Vin.
Why such a big difference between cases 1 and 2? Thanks for any tips.