Physical layout is as critical to good power-supply operation as the semiconductor devices and passives that are selected. Poor circuit layout can ruin an otherwise great design. Luckily, most mistakes have been made before and you can learn from them! This presentation focuses on some of the most common layout mistakes in DC/DC and AC/DC power supplies. For each issue, we will review the likely symptoms, root cause and describe how to optimize the layout to avoid the problem. For each mistake we will also discuss some related tips and tricks to make you power-supply layouts the best they can be.