What is Decoupling Capacitor and Its Working

The common issue facing all digital electronics today is the noise. These are occurred due to faster interfaces as well as the consumption of low-power in devices from power & signal lines. Fortunately, this noise can be decreased with the help of decoupling to separate one circuit to others within a system. The passive component like the decoupling capacitor is the most frequently used one in different circuits like an amplifier, complex filter, analog & power electronic circuits. This article discusses an overview of this capacitor and its working.

What is a Decoupling Capacitor?

Definition: Decoupling capacitor is one kind of capacitor, used to decouple or isolate two dissimilar electronic circuits or decouple the signals from AC to DC. This capacitor plays a key role while eliminating the noise, power distortion and protects the system by supplying pure DC supply.

Decoupling Capacitors
Decoupling Capacitors

In logic circuits, the decoupling method is essential. For instance, if a logic circuit operates with 5V supply voltage if the voltage supplies above 2.5 volts then it will call as high signal. Similarly, if the voltage supplies below 2.5 volts then it will call as low signal. If there is noise within the voltage supply, it will activate high and low within the circuit, thus the DC Coupling capacitor is extensively used in logic circuits.

Decoupling Capacitor Design

The decoupling capacitor placement can be done parallel to the power supply. So it is connected in between the power supply & the load in parallel. Once the power supply is given to the circuit, then the reactance of this capacitor is infinite on DC signals. So it doesn’t permit DC signals to moves toward the ground. But, the reactance of AC signals is less, so they flow throughout the capacitor and moves toward the ground.

Decoupling Capacitor Circuit
Decoupling Capacitor Circuit

Decoupling capacitor working is, it supplies a low impedance lane for high-frequency signals on the supply so that DC signal can be cleaned up. In this way, this capacitor decouples the signals from AC to DC.

Normally for these capacitors, the capacitor values must be in 10nF & 100nF. But, usually, 100nF value capacitors are used in different applications. So, a ceramic capacitor is the most used decoupling capacitor.


How to Select a Decoupling Capacitor?

When choosing a decoupling capacitor for different applications, some electrical requirements need to consider while designing like the low-frequency of the AC signal, resistor’s resistance value.

This capacitor selection can be done based on its value. Based on the application, there are certain standards to select the capacitor value. The value of the capacitor with less frequency noise must be between 1 µF to 100 µF. Similarly, the value of the capacitor with high-frequency noise must be between 0.01 µF to 0.1 µF.

The connection of these capacitors can be done always directly to the ground plane of low impedance for its efficient operation.

Difference between Decoupling and Bypass Capacitor

The difference between decoupling and bypass capacitor includes the following.

Decoupling Capacitor

Bypass capacitor

A capacitor that is used for decoupling one element of an electrical circuit from other circuits is known as a decoupling capacitor. This capacitor shorts AC signals toward ground terminals, so that AC noise present on a DC signal can be detached and generates a pure and cleaner DC signal.
This capacitor is designed for smoothening the signal by stabilizing the unclear signal. The designing of this capacitor can be done to shunt the noise signals.


The arrangement of this capacitor can be done between the power supply & the load parallel with each other This capacitor can be connected between the Vcc pins & the GND pin to decrease the noise of supply & the outcome of the spike over the lines of supply.
The capacitance value of this capacitor can be calculated using this formula C = 1/2πfC. The capacitance value of this capacitor can be calculated using this formula C = 1/2πfC.
The values of this capacitor range from 0.01 µF to 0.1 µF The common values of this capacitor are 1µF & 0.1µF
This capacitor uses are Isolating two different circuits; remove the distortion of power, noise and defend the system. The applications of this capacitor are used between amplifier & loudspeaker to get clear audio, DC/DC converter, signal coupling, signal decoupling, LPFs, and HPFs.

Capacitors used in Decoupling Applications

There are different types of capacitors used in the applications of decoupling or bypassing. The characteristics of these can be changed based on the dielectric material used, structure, physical size, linearity, temperature stability, cost & voltage rating. The different types of capacitors used in these applications are ceramic, aluminum electrolytic and tantalum capacitors.


1). What is the function of the decoupling capacitor?

This capacitor is used to suppress high-frequency noise within power supply signals

2). What are the capacitors used in decoupling applications?

They are tantalum, ceramic as well as aluminum electrolytic.

3). What is the value of the decoupling capacitor?

The values range from 0.01 µF to 0.1 µF

4). What is the difference between the bypass and decoupling capacitor?

The bypass capacitor shunts the noise signals & the decoupling capacitor smoothens the signal through stabilizing the unclear signal.

5). How to test a capacitor?

The testing of a capacitor can be done using a multimeter.

Thus, this is all about an overview of the decoupling capacitor. These capacitors are frequently used for decoupling the electrical circuit from the supply. It functions properly using some components which use regulated power source. The best examples of this are microprocessors and microcontrollers. If the program is loaded into the processor then it will skip the instructions. The logic circuits are also responsive to voltage power supply voltage. So it should be regulated well for secure operation due to this reason, these capacitors are utilized within the circuit to stabilize the voltage power supply. Here is a question for you, what is the capacitance?