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IC 7805 Voltage Regulator

Updated on May 12, 2014

IC 7805

IC 7805 is one of the popular Integrated circuit that can be found in almost all electronic circuits. IC 7805 is used for voltage regulation. It is gives a constant voltage output for a wide range of varying input voltages.

Why IC 7805 is called so?

IC 7805 belongs the family of 78xx. It is also called as LM 7805, L 7805, MC 7805 etc. the last two digits (05) denotes the output voltage of the IC.

Other ICs of 78xx series

Number
Output Voltage (V)
7806
6
7808
8
7810
10
7812
12
7815
15
7818
18
7824
24

About IC 7805

As mentioned earlier IC 7805 IC is used for voltage regulation in an electronic circuit. It is a three pin IC that gives a constant output voltage of 5V irrespective of the varying input voltages. The maximum value of input voltage that the IC can withstand is 24 volts. The output of the IC will be a constant 5V up to the input voltage of 24V (i.e.) any increase in the input voltage will not affect the output voltage of IC 7805. It will be always supplying a constant 5 volt even if the input voltage rises above 5 volts. IC 7805 comes with a provision to add heat sink. When IC 7805 is operated above 7 volts it requires heat sink. When it is operated above 7 volts, it produces more heat and strictly requires a heat sink for the proper dissipation of heat energy produced.

Why voltage regulation is required in an electronic circuit?

IC 7805 is used to maintain a steady state voltage level in an electronic circuit. Voltage fluctuations in a circuit may damage the circuit components and reduce the life of the equipment. Hence it is essential to supply a constant voltage to the circuit.

For example, consider that we need to provide Vcc (5V) to a microcontroller. If we are supplying the required voltage directly from a rectifier, any voltage variations will directly affect the micro controller thereby damaging it. In order to avoid this we can include IC 7805 to the circuit to provide a constant and steady voltage output.

Pin No
Function
Name
1
Input voltage (5V-18V)
Input
2
Ground (0V)
Ground
3
Regulated output; 5V (4.8V-5.2V)
Output

Pin out Configuration of IC 7805.

The pin out configuration of IC 7805 is shown in the diagram.

IC 7805 Pin out configuration

The pin 1 acts as the input terminal (5V to 24V).  The pin 2 acts as the Ground terminal (0V).  The pin 3 acts as the output terminal (constant regulated 5V).
The pin 1 acts as the input terminal (5V to 24V). The pin 2 acts as the Ground terminal (0V). The pin 3 acts as the output terminal (constant regulated 5V).

7805 Connection

In the above circuit C1 = 0.33 uF and C2 = 1 uF.
In the above circuit C1 = 0.33 uF and C2 = 1 uF.

Connection diagram

IC 7805 must be used in the circuit as shown in the circuit. It consists of two capacitors C1 and C2 connected across the input and output terminals respectively.

Why capacitors are connected across the input and output terminals of 7805?

The capacitor C1 connected across the input terminal and the ground eliminates the inductive effects due to long distribution leads. The capacitor C2, connected across the output terminal and the ground improves the transient stability.

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Comments

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    • goodnews11 profile imageAUTHOR

      OSBERT JOEL C 

      4 years ago from CHENNAI

      Thank you so much eugbug. You have added a very useful point on your comment. As you said it will really save money over years. Thank you for commenting.

    • eugbug profile image

      Eugene Brennan 

      4 years ago from Ireland

      There are also drop in replacement, switching versions of the 78XX series of voltage regulators. I haven't used them, but being more efficient, they run much cooler especially in applications where a large voltage drop and/or higher current demand is required. So a small heatsink would be required. It could be a good idea to use them in burglar alarms or other devices which run constantly (it would save a little money over the years!)

      Voted up and useful for those with an interest in basic electronics.

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