Where is capacitor used

Most electronic devices employ capacitors that are an invaluable part for electronic products. Capacitors are very popular among many applications like electronic circuits, power circuits, and power supply units. The capacitor is referred to as Big Three Passive Components together with resistance and coil, which are the basics of electronic circuits. Passive components are an electronic part which receives the power to consume, store, and supply.

Unlike integrated circuits IC , it has no active operation where low power is amplified to constantly output the power. You might as well regard capacitor as a simple part to receive and supply the electricity. However, more importantly, such passive components are indispensable parts to accurately perform active components.

Capacitor is basically formed from an insulator and two metal plates that are attached on the both sides of the insulator. Insulators do not carry current. The insulator used for capacitors is specifically called as dielectrics. While the electricity is flowing, the positive and negative charges are transferred within the conductor.

Charged with the electricity, the flow of the charge is started, but it is blocked since there is an insulator between metal plates. Then, the charges are built up on only one of the two metal plates. Meanwhile, another metal plate attached to the insulator has opposing charge. Thus, capacitors have a structure to store the electricity between the two metal plates. For materials of insulator, gases, oils, ceramics, and resin are used.

As for shapes of the metal plates, there are a wide variety of types with parallel plates, foil wrapping, multi-layers, and so on.

The amounts of stored charges as well as the supported frequencies are different depending on the types of insulators or the structure of capacitors. In some cases, like the flash circuit of a camera, you need a buildup of energy and then a sudden release. This is exactly what a capacitor does.

In the camera circuit, you press the button to take the picture and a charge is released to the capacitor. Once it has reached the peak level, the capacitor discharges, causing a flash. Ross Garner began writing professionally in He now works for "Scottish Television" online.

Earlier this year Garner graduated from the University of Strathclyde with a Bachelor of Arts Honours degree in journalism and creative writing with English. List of Uses for Capacitors. How to Use a Magnet to Create Electricity.

How to Make a Simple Oscillator. How to Revive Lithium Ion Batteries. Electronics Projects Using or IC. How to Calculate Instantaneous Voltage. If the DC components of the signal at the output of the first stage were present at the input of the second, then the bias and other operating conditions of the second stage would be altered. Even when using operational amplifiers where the circuit has been designed to provide small offset voltages, it is often wise to use coupling capacitors because of the high levels of DC gain present.

Without a coupling capacitor, the high levels of DC gain could mean that the operational amplifier would run into saturation. For capacitor applications of this nature it is necessary to ensure that the impedance of the capacitor is sufficiently low. Normally the output impedance of the preceding circuit is higher than the one it is driving, except for RF circuit, but more of that later.

This means that the value of the capacitor is chosen to be the same as the impedance of the circuit, normally the input impedance of the second circuit. This gives a drop in response of 3dB at this frequency. In this application, the capacitor is used to remove any AC signals that may be on a DC bias point, power rail, or other node that needs to be free of a particular varying signal.

As the name of this capacitor use indicates, it used to decouple the node from the varying signal on it. In this circuit there are two ways in which the capacitor is used for decoupling. C3 is used to decouple any signal that may be on the voltage rail. This type of capacitor must be able to withstand the supply voltage as well as supplying and absorbing the levels of current arising from noise on the rail.

Also during switch-off, when the power is removed, large levels of current may be drawn from this capacitor dependent upon its value. Tantalum capacitors are not suitable for this position. Decoupling is also provided by the combination of capacitor and resistor, C4, R5. This ensures that the collector signal does not leak through on the signal rail.

The time constant of C4 and R5 is generally the dominating factor and the time constant should be chosen to be longer than the lowest frequency anticipated. The type of decoupling used with C5 serves to isolate that particular stage well from any noise on the rail as well as preventing noise from the circuit passing onto the supply rail.

During switch-off, current from the capacitor is limited by the resistor R5. RF coupling and decoupling follow the same basic rules as those needed for the ordinary coupling and decoupling capacitors. Circuits like the one shown for the standard coupling and decoupling are often used, and they perform in basically the same way. However, when using capacitors for RF applications, it is necessary to consider their RF performance. This can be different to the performance at lower frequencies.

Normally electrolytic capacitors are not used - their performance falls with increasing frequency, and they are seldom used for applications above about kHz. Ceramic capacitors are particularly popular as they possess a good RF performance, especially the surface mount MLCC capacitors.

The series inductance present in all capacitors to a greater or lesser degree makes itself felt at some frequencies, forming a resonant circuit wit the capacitance. In general, ceramic capacitors have a high self resonant frequency, especially the surface mount capacitors that are very small and have no leads to introduce any inductance.

Some other types of capacitor could be used, but ceramic capacitors are most widely used in this application. This is effectively the same as a decoupling capacitor, but the term is normally used in conjunction with a power supply.

When an incoming line signal is taken through a transformer and a rectifier, the resulting waveform is not smooth. It varies between zero and the peak voltage. If applied to a circuit, this is most unlikely to operate as a DC voltage is normally needed. To overcome this, a capacitor is used to decouple or smooth the output voltage.

In this use, the capacitor charges up when the peak voltage exceeds that of the output voltage, and supplies charge when the rectifier voltage falls below the capacitor voltage. Normally relatively large values of capacitance are required to enable the required level of current to be supplied. As a result, the most widely used form of capacitor for this application is the electrolytic capacitor.

In this application a capacitor can be used with a resistor or inductor in a resonant or time dependent circuit. In this function the capacitor may appear in a filter, oscillator tuned circuit, or in a timing element for a circuit such as an a-stable, the time it takes to charge and discharge determining the operation of the circuit.

LC or RC oscillators and filters are widely used in a host of circuits, and obviously one of the major elements is the capacitor. In this particular capacitor use, one of the main requirements is for accuracy, and therefore the initial tolerance is important to ensure that the circuit operates on the required frequency. Temperature stability is also important to ensure that the performance of the circuit remains the same over the required temperature range.

In this particular capacitor application, the charge held by the capacitor is used to provide power for a circuit for a short while. In the past small rechargeable batteries may have been used, but they often suffered from issues of memory effects and life limitation, so capacitors can offer a viable alternative.

Nowadays, super capacitors offer huge levels of capacitance and they are now sufficiently large to enable many circuits to remain powered during periods where the mains power is unavailable.

They are relatively cheap and offer a great level of performance.