What is the difference between a linear and a switching power supplies? Could you describe some applications of each?

Power supplies (regulators) are one of the most important devices used in the electronics. A power supply or regulator provides a constant dc output voltage that is independent of the input voltage, output load current, and temperature.

1. Describe in your own words the stages of a power supply.
2. What is the function of the transformer, the rectifier, the filter?
3. What is the difference between a linear and a switching power supplies? Could you describe some applications of each?