Correct capacitor choice - OT

[mister_e]

Usually, the ouput one don't need to be as this big because the regulator have to do his job. Usually 10uF tantanlum + 0.1uF Ceramic are enough and must be sit as close as you can of your regulator output. NOW, depending of your circuit, you may need something bigger close to some device to reduce the noise comming from XYZ device. Let's say you have some 'high current driver' you may need to add some capacitor of different value close to them... also called bypass capacitor. Usually they are listed in the datasheet.

Generally, i use 10uF Tantalum + 0.1 uf Ceramic at the regulator output, 10uF tantalum + 0.1 uF ceramic close to the PIC +0.1 uF ceramic close to each and every IC in the circuit + a/some bigger(s) one(s) if needed for some specific reason. Capacitor are there to avoid your ICs to generate noise on the supply line. As they are called bypass capacitor, they will bypass the noise where they're install. Closer to your IC they will be, less are the chance to introduce noise in the rest of your circuit. In conjunction with a good groound plane (or 2 if analog is involved) you reduce your chance to generate noise on the supply AND generate 'RF' (EMI) noise.

At the regulator input... same thing apply 10uF Tantalum+0.1uF ceramic installed really close to the regulator is a good practice. Depending where your DC is comming from, you may need to add a bigger capacitor to reduce the ripple. If it's comming from a DC wall-mount transformer, they're already some capacitor mounted inside but adding something in a range of 100-1000 uF maybe of help. Better if you use some LC filter. Even a RC filter is really great too. A low value resistor in serie (let's say 4.7 - 10 ohm) + 470 uF may kill a lot of ripple... in fact better noise rejection than using a simple 470uF capacitor. Also, the low value resistor may react as a fuse.. no it's not a fuse but may act as.

You can do a search on googgle with 'Ground boucing' 'Ground plane' 'Bypass capacitor' and you'll find more info that you need.