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Voltage Regulators
Input
Common
Output

Pin Layout

A voltage regulator is an integrated circuit that can be used to produce a steady DC power supply of a specific voltage. The circuit shown below is of a 7805 voltage regulator which produces an output voltage of 5V from an input voltage of between 10V and 35V.

 

 

Uses

A common use is where a voltage of 5V is required for digital circuits when only a higher one is available. A voltage of 5V is often required in digital circuits (logic gates) and PIC chips.

 

Sometimes different parts of circuits need different voltages to work properly. This could be achieved by using different voltage batteries although this would take make the product larger and heavier. A more efficient way would be to use only one battery and use voltage regulators to provide lower voltages.

 

As batteries discharge their output voltage gradually drops. Provided the input voltage doesn’t drop below a certain voltage the output voltage will remain at the required voltage.

 

As you may have noticed, when you connect a heavy load to a battery its output voltage actually drops, this is because it has an internal resistance. Using a voltage regulator prevents this effect and keeps the output fixed to 5V irrespective of the load (to a certain point).

Circuit to produce output voltages of 24V and 5V from only one battery.

Input voltage from power supply

Voltage Regulator

Metal heatsink

Heatsinks

When voltage regulators are in use they can produce waste heat, if they get too hot then the regulator can be damaged.

 

A metal heatsink is sometimes fitted which takes the heat away from the regulator to take the heat away.

Vout

0V

Vin

0V

24V

0V

5V

24V