I just built a basic power board for a project that needs a +5V, GND, -5V outputs. Current requirements are tiny (100ma max, and <<10ma normal)
Here is my schematic: (Pretty much straight from the 7805 datasheet)
The problem is that both +5 and -5 lines ripple by roughly .25V. Oscilliscope reading:
I tried adding some electrolytic caps (47uf) to smooth things, but it had almost no effect.
What do I need to do to smooth these lines? I'm using them for an ADC that needs to take accurate readings between 0 and 3.3V, and this is destroying accuracy. I'd like to get this ripple down by an order of magnitude or 2.
Here is my schematic: (Pretty much straight from the 7805 datasheet)
The problem is that both +5 and -5 lines ripple by roughly .25V. Oscilliscope reading:
I tried adding some electrolytic caps (47uf) to smooth things, but it had almost no effect.
What do I need to do to smooth these lines? I'm using them for an ADC that needs to take accurate readings between 0 and 3.3V, and this is destroying accuracy. I'd like to get this ripple down by an order of magnitude or 2.