Old app note from Fairchild Semiconductor about external component effects on LDOs. Link here (PDF!)
Low drop-out (LDO) regulators are one of the basic building blocks of most power supplies used in today’s electronics. Their ease of use, low cost, and small size makes them ideal in portable and handheld applications. They are available in wide variety of voltage & current levels with their primary function, to provide power to low-voltage digital circuits. The only other necessary components are external capacitances, which, in conjunction with the LDO, create a complete power solution. This application note reviews the effect of these components and their phase shifts on the LDO’s loop stability and show how to tailor the compensation to obtain a stable circuit.