Capacitor Guide

Basics of capacitors [Lesson 5] Applications of ceramic capacitors

This technical column describes the basic facts about capacitors.
This lesson describes the different types of ceramic capacitors.

Lesson 5: Applications of ceramic capacitors

Ceramic capacitors are used for all types of circuits in a number of applications.
There are four main capacitor applications that are described in detail below: coupling, decoupling, smoothing, and filtering.


Capacitors used in coupling exploit the characteristic of capacitors to only transmit AC components and not transmit DC components, and are used to extract AC components from DC + AC components.
As the operating conditions of transistors, ICs and other active elements on circuits vary, it is necessary to extract only the required AC signal after setting the optimal operating conditions for each circuit.
Coupling refers to linking circuits together, and, as their name suggests, coupling capacitors act as the intermediary for linking circuits together.

Figure 1. Capacitors for coupling


Power lines on circuits have capacitance and inductance components. If these components cause the voltage variation on power lines to increase, operation of the circuit becomes unstable. In extreme cases, fluctuations in the power source can become superimposed on the signal line, causing transmission of incorrect signals.
Decoupling capacitors are used to pass noise coming in from the power source to the ground terminal, while at the same time continuously supplying stabilized current to combat sudden changes in load current on ICs and other circuits.
As shown in Figure 2, even if the noise is superimposed on the line, unwanted noise can be passed to the ground terminal via decoupling capacitors.

Figure 2. Capacitors for decoupling


Smoothing capacitors suppress ripples that are generated even after rectification with a power circuit to smooth-out signals so that they approach direct currents.
When smoothing capacitors are installed after rectification, excess voltage is stored in the capacitor during high-voltage periods and released during low-voltage periods, thereby eliminating fluctuations in voltage.

Figure 3. Capacitors for smoothing


Capacitors are combined with resistors and inductors to create filters that only transmit signals of a particular frequency.
Different filters can be used depending on the frequencies you want to transmit, including low-pass filters that filter out low-frequency components and high-pass filters that filter out high-frequency components.

Murata Manufacturing Co., Ltd. Component Division Sales Engineering Department N.W

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