Capacitors are a common component that can be found across many applications.
How capacitors are used in these applications varies, depends on how they’re utilized in a circuit. They may be used in series or in parallel and as energy storage or in amplifiers. Here’s an introduction to these concepts.
Capacitors in Series
When capacitors are connected in series, the total capacitance is less than the value of the lowest individual capacitance. Thus, the formula for calculating the total series capacitance is represented as:
Series capacitors also have the characteristic of having equal charges across the connection, where:
Capacitors in Parallel
When capacitors are connected in parallel, the total capacitance is the sum of the capacitances making the total capacitance greater than that of any individual capacitors capacitance. The formula for calculating the total capacitance is given as:
Parallel capacitors also have the characteristic of having similar voltages across them, meaning that:
And its total charge is the sum of the charges of its members given as:
Coupling and Decoupling Capacitors
Decoupling capacitors are used to oppose quick changes of voltage in the circuit. If the input voltage suddenly drops or spikes, the capacitor provides or absorbs energy to stabilize the circuit.
Decoupling capacitors are also called bypass capacitors because they are used to filter out voltage spikes and pass through only DC component of the signal, bypassing the power source when needed.
While decoupling capacitors are connected in parallel to the signal path to filter out the AC component, coupling capacitors, on the other hand, are connected in series to the signal path and are used to filter out the DC component in a signal. Both are used in analog and digital applications.
In analog circuits, coupling capacitors are greatly used in amplifiers. Making it block the incoming AC signal from interfering with the bias voltage applied to the base of the transistor. In digital circuits, especially in communications systems, coupling capacitors are used to block DC signals in the transmission lines. The presence of a DC signal across a transmission line means that energy is wasted dissipated as heat.
Capacitors are devices that can store electrical energy in the form of electrical charge accumulated in their plates. Connecting a capacitor to a power source makes it accumulate energy that can be released when the power source is disconnected, similar to a battery. The only difference is that a battery uses electrochemical process to store energy, while a capacitor simply stores charge.
This function of the capacitor is applied in many devices such as audio equipment, UPS, camera flash, etc. Electronic camera flashes mostly use xenon flash tubes. Before a shot is taken, the internal capacitor is charged for the flash to be ready for use. When the shutter button is pressed on the camera, the capacitor is instantly discharged through the tube. The energy is converted into a flash of light, a process that lasts only about 1 millisecond. After the flash is used, it takes some time for the capacitor to recharge before the next shot can be taken.