Basic Electronics On The Go - Applications of Capacitors

From http://www.electronicshub.org/applications-of-capacitors/

Introduction

Capacitor is one of the passive components and it stores energy in the form of electrical charge. Capacitor charges and discharges the charge depending on the circuit operation. It is used mainly in electronic and electrical circuits to perform different tasks, such as smoothing, filtering, bypassing, noise reduction, sensing capabilities  etc.

 First of all we need to choose which type of capacitor is suitable for a particular application. Choosing of capacitor type depends on some factors. The factors which influences in choosing type of a capacitor for a specific application are given below,

Capacitance Value Ranges: Each type of capacitor available in a specific range. Depending on application we need to choose a required range of capacitor.

Working Voltage:Some types of capacitors have low working voltages and some more type of capacitors have high working voltages. Depending on the application we need to choose the capacitor voltage.

Polarization:Tantalum and electrolytic capacitors are polarized and also they operate with a voltage in one direction. So polarization is one of the important factors while choosing the capacitor.

Tolerance: The close tolerance value capacitors are needed to choose for applications like oscillators and filters where the capacitor value is critical. But in some type of applications like coupling and de-coupling the value of capacitor is not critical.

Temperature Coefficient:Capacitance value varies with temperature in some type of capacitors and some capacitors like silver mica, ceramic are stable with varying temperatures. So depending on application one can select the capacitor.

Leakage Current: High level insulation is needed in some applications but in some applications it is not necessary. Electrolytic capacitors have poor leakage performance. Leakage current is also considerable factor while choosing the capacitor for application.

Cost: The cost is the basic driving parameter for all applications. Because everyone want to have high performance with low cost.Today, all the high performance capacitors are available for low cost in surface mount packages.

Table of capacitor applications

(click on table to see bigger view)

Filter Applications

Capacitors are used as main elements in frequency selective filters. All the filter designs are used for the high performance and frequency based applications,by selecting the proper components and quality required. Some of the filter topologies are given below.

•  High Pass Filter (HPF)
•  Low Pass Filter (LPF)
•  Band Pass Filter (BPF)
•  Band Stop Filter (BSF)
•  Notch Filter (NF)
•  All Pass filter (ALF)
•  Equalization Filter (EF)

Decoupling/By-Pass Capacitors

Decoupling capacitors are used in digital electronics to protect the microchips from the electrical noise on power signals. The main role of decoupling capacitors is to reduce the noise in the circuit. These capacitors are placed very close to the microchips in the circuits to remove noise from the surroundings. These capacitors are also provides extra energy to the IC’s and also remove disturbances to the logic signal.

Coupling or DC Blocking Capacitors

The coupling or DC blocking capacitors are used in the applications where the AC and DC signals  need to be separated. These types of capacitors will allow only AC signals and blocks the DC signals. Here the capacitance value of a capacitor will not affect the coupling applications. But the performance of these capacitors is high in the applications if the reactance of a capacitor is high value. The main use of these capacitors is to block the DC currents from the signal. These types of capacitors are used to pass AC signals for coupling of one electronic circuit to another circuit.

Snubber Capacitors

Snubber capacitors are used in the circuits where high inductance load is driven. In high inductance circuits, such as in transformers and in motors the stored energy is discharged suddenly. Due to this effect other components in the circuit may damage and also large power spikes are obtained in those circuits. To avoid these problems we use capacitors across the high inductive components in the circuits.Due to this process the capacitors avoid voltage spikes and also they provide safety to the circuit.

Low power circuits also use these snubber capacitors to avoid voltage spikes, which are created from undesirable radio frequency (RF) interferences.These snubber capacitors are also used in parallel to the interrupt components, in the high voltage circuits to avoid circuit breaker problems by producing equal voltage distribution between those components.

Pulsed Power Capacitors

Generally a capacitor is small energy storage component. Large capacitors and capacitor banks are used where a lot of energy required within a short period of time. Capacitor banks store the lot of energy for the applications, such as particle accelerators, pulsed lasers, radars, max generators, fusion research and rail guns. A normal application for pulsed power capacitors is used in a flash on disposable camera which charges up and discharges quickly through its flash.

Resonant or Tuned Circuit Applications

To design filters we use capacitor, resistors and also inductors. In this design some combinations of components are used, to amplify the resonant frequency signals. Here the low power signals are amplified to the high power signals, at resonant frequency, as tuned filters or oscillators. But in designing the resonant frequency circuits we take much care about the component combinations because some of the combinations  may damage the operation and also fail quickly.

Capacitive Sensing Application

The capacitive sensing is a technique in detecting the change in capacitance value, change in the distance between the plates, change in dielectric and change in the area of capacitor plates. Capacitive sensing is a technique which is recently used in advanced consumer electronic circuits. Capacitive sensors are used in different applications such as position, fluid level, humidity, acceleration and manufacturing quality control etc.

Capacitor Safety

We need to take some safety precautions about capacitors. Capacitors are storage devices, which store electrical energy from small amounts to large amounts. Due to this high energy we can observe electrical charge even though the power is disconnected. Sometimes these high energy capacitors may damage the circuit components. The best thing to avoid these problems is to discharge the capacitors before use in the electrical circuits.

If the voltage to the polarized electrolytic capacitors are reversed then these capacitors may fail in the circuit operations. The breaking of dielectric material also causes failure of the capacitors even though they are used in high voltage and high power applications.