Why Capacitor need to use with IC 78XX Series Voltage Regulators?

You may notice, that when IC 7805, IC 7809, IC7812, or IC 78XX series voltage regulator ICs are used in electronic circuits, two capacitors are connected with them, one connected to the input and another connected to the output. So you may wonder, why these capacitors are used.
Today we are going to know why capacitors need to connect with IC 78XX series voltage regulators.

Why IC 78XX series ICs are used in Electronic Circuits?

IC 78XX series ICs are used in electronic circuits for voltage regulation purposes. Voltage regulation means they always keep a constant voltage level in output even during the voltage fluctuations in the input. So these ICs are used to provide constant regulated voltage. They also used to step down the DC voltage. IC 78XX series ICs can work with DC supply that's why they are used in DC circuits.

Capacitor Need with IC 78XX

The main purpose of using input and output capacitors with IC 78XX is to remove or filter the AC noise or ripples. Generally, when the regulator IC is situated more than 10 inches away from the power supply source, we need to connect capacitors.

When the distance between the regulator IC and the power supply source is greater than 10 inches then the conductors between them act as an antenna. So unwanted noise is produced.



IC 78XX series voltage regulators can work more efficiently when there is no AC noise or ripple on the line. They need a pure DC signal to work properly.

These capacitors are called bypass capacitors. When AC noise is produced on the line, the capacitor creates a short circuit or provides a low-impedance high-frequency path to the AC noise signal. Thus it removes the AC noise from the circuits. These input and output capacitors are also called decoupling capacitors.

So, the capacitor used with the IC 78XX series,

1. To filter or remove AC noise or ripples
2. To improve the transient responses
3. Protection against Surges
4. To increase the stability
5. To remove the deposited charges from the IC terminals during the regulation.
6. To increase the reliability of the circuit.

Which Capacitor should be used?

If the power source is 12V and the output voltage of the regulator is 5V then the 0.33 micro-farad input capacitor and 0.1 micro-farad capacitor are best for the circuit. As the ceramic capacitor is available with small values, so in this case ceramic capacitor can be used.

Ceramic capacitors are best for noise filtration applications. So, mostly ceramic capacitors are used with voltage regulator ICs.


Read Also:

• Why all Electronic Devices Works on DC not AC?
• What is Vcc, Vss, Vdd, Vee in Electronics? Differences and Full Forms
• Why NPN Transistors are mostly used than PNP Transistors?
• Why CPU has so many power supply pins (e.g. Vcc, Vss)?
• Why Capacitor is must use in all Timing Circuits?

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