Electronics 01
Does My 7805 Need a Heatsink? Work It Out in Two Lines
A 7805 needs a heatsink above about 1.5 W. Work out the power, the junction temperature and the heatsink you need from the datasheet numbers.
heat sinks
Electronics 02
LM317 Formula Explained, With Worked Examples
Vout = 1.25(1 + R2/R1) + Iadj R2. Where the LM317 formula comes from, how to pick R1 and R2, why it needs 3 V of headroom and when it needs a heat sink.