Suntan Blog

Ceramic capacitors are available now in three main types although other styles are available:

• leaded disc ceramic capacitors for through hole mounting which are resin coated
• multilayer surface mount chip ceramic capacitors
• Specialist microwave bare leadless disc ceramic capacitors that are designed to sit in a slot in the PCB and are soldered in place

Although it is possible to obtain other types of ceramic capacitor, these are the main types that can be found today. Of these the surface mount variety is used in the greatest quantities by far because of the manufacturing methods used these days for electronic equipment.

Electronic capacitors are one of the most widely used electronic components. These electronic capacitors only allow alternating or changing signals to pass through them, and as a result they find applications in many different areas of electronic circuit design. Suntan supply a wide variety of types of capacitor including electrolytic, ceramic, tantalum, plastic, sliver mica, and many more. Each capacitor type is introduced in www.suntan.com.hk.

The choice of the correct capacitor type can have a major impact on any circuit. The differences between the different types of capacitor can mean that the circuit may not work correctly if the correct type of capacitor is not used.

When measured at room temperature (25°C ± 5°C) and at a frequency of 0.1 to 1 Megahertz, the minimum capacitance shall not be greater than that specified at minimum setting with a +10% tolerance and the maximum capacitance shall not be less than that specified maximum setting with a - 10% tolerance.

1.Extremely large capacitance to volume ratio, small size, low ESR.

2.Available in hundreds, or thousands, of farads. A relatively new capacitor technology.

3.Often used to temporarily provide power to equipment during battery replacement.

4.Can rapidly absorb and deliver larger currents than batteries during charging and discharging, making them valuable for hybrid vehicles.

5.Polarized, low operating voltage (volts per capacitor cell). Groups of cells are stacked to provide higher overall operating voltage.

Although the construction techniques and materials used to manufacture multilayer ceramic and tantalum capacitors are completely different, the basic applications still remain the same. Capacitors in the 0.1 - 22µF range are used mainly for digital circuit decoupling and filtering. Acting as local supplies of charge, capacitors assist power supplies in remaining at a constant DC voltage despite the continuous switching of digital signal circuitry. Capacitors also function as simple, single pole filters and can be used in conjunction with other devices (resistors and inductors) to create higher order filter circuits.

As much as tantalums and ceramics are both capacitors, they do have many different properties. The case sizes and capacitance values available will first be studied. The impedance curves, the parasitic inductance (ESL) and equivalent series resistance (ESR) for each of the technologies will also be outlined. Then the electrical performance under a variety of conditions, such as temperature and DC bias, will be examined.

Natural mica has to be carefully selected because some samples do contain impurities including, iron, sodium, ferric oxide, and lithium. This introduces some variability into any mica that might be used for capacitor manufacture and therefore it must be carefully inspected and classified. This is one of the reasons why silver mica capacitors are more expensive than other types which have less manual intervention.

Mica is chemically very stable and chemically inert. Mica does not react with oil, water, many acids alkalis, and solvents. As a result of this, ageing does not occur to any major degree, and the variations of water vapour in the atmosphere do not cause undue variations in the overall capacitor performance.

Although more costly than other dielectrics, mica is an ideal form of dielectric for very high performance capacitors such as silver mica capacitors.

The function of capacitors in a circuit is often explained with comparison to a water tank.  When a capacitor is compared to a water tank, the battery can be considered as the pump filling the tank with water.

On the circuit, water is similar to dislocation, and the water quantity in the tank can be expressed as the changed quantity pumped in to the capacitor.  Thus, the capacitor’s area corresponds to the dislocated quantity as the tank’s area corresponds to water quantity.

We know that a long and narrow vertical tank can hold just as much water as the short, wide and horizontal tank can. However, the vertical tank has more pressure due to the water than the horizontal one. In the same idea, we can think that for a large capacity, there is a low voltage, and short and wide capacitor, and for a low capacity, there is a high voltage, and long and narrow capacitor.

When the capacitor is connected to the circuit while receiving energy from active components(Battery), one electrode of the capacitor bears a positive electric charge, and the other electrode becomes negative.  The electric charge on the electrode will conduct the opposite charge on the whole.  The electric charge conducted like this is called Permittivity.

Transducers

Potentiometers are also very widely used as a part of displacement transducers because of the simplicity of construction and because they can give a large output signal.

Computation

In analog computers, high precision potentiometers are used to scale intermediate results by desired constant factors, or to set initial conditions for a calculation. A motor-driven potentiometer may be used as a function generator, using a non-linear resistance card to supply approximations to trigonometric functions. For example, the shaft rotation might represent an angle, and the voltage division ratio can be made proportional to the cosine of the angle.

The most common type of varistor is the metal oxide varistor, or MOV. This contains a mass of zinc oxide grains, in a matrix of other metal oxides, sandwiched between two metal plates (the electrodes). The boundary between each grain and its neighbour forms a diode junction, which allows current to flow in only one direction. The mass of randomly oriented grains is electrically equivalent to a network of back-to-back diode pairs, each pair in parallel with many other pairs. When a small or moderate voltage is applied across the electrodes, only a tiny current flows, causes by reverse leakage through the diode junctions. When a large voltage is applied, the diode junctions break down because of the avalanche effect, and a large current flows. The result of this behaviour is a highly nonlinear current-voltage characteristic, in which the MOV has a high resistance at low voltages and a low resistance at high voltages.

If the size of the transient pulse (often measured in joules) is too high, the device may melt, or otherwise be damaged. For example, a nearby lightning strike may permanently damage a varistor.

Important parameters for varistors are response time (how long it takes the varistor to break down), maximum current and a well-defined breakdown voltage. When used in communications lines (such as phone lines used for modems), high capacitance is undesirable since it absorbs high frequency signals, thereby reducing the available bandwidth of the line being protected.

The electronics circuits and modules section of this website aims to provide a pot-pourri of electronics design ideas and circuits that can be used within electronics hardware designs. It focuses on providing easy to use designs that can be implemented into electronic product designs, using easy to use formulae and design ideas.

Resistors and capacitors can be considered as the staple components used in electronic circuits. While resistors and capacitors are most commonly used with other active devices, they may also be used on their own in resistor or capacitor circuits, or circuits using combinations of the two.