Suntan Blog

A varistor is a type of resistor with a significantly non-ohmic current-voltage characteristic. The name is a portmanteau of variable resistor*, which is misleading since it is not continuously user-variable like a potentiometer or rheostat, and is not a resistor but in fact a capacitor. Varistors are often used to protect circuits against excessive voltage by acting as a spark gap.

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.

Suntan has specially developed a new series of X2 capacitors TS08S series with metalized polypropylene films for interference suppression. These capacitors are designed for voltages of 275VAC, specified for temperatures from -40 to +100 °C, capacitance range extended from 1 nF to 2.2 µF, or customized as requested. This new X2 series provide interference suppression with CE & TUV and UL safety approvals. Their Typical applications include power supplies of all types, lamp ballasts and EMC filters.

Currently TS08S is Suntan strong promoting product, with our best support always. Welcome to send new inquiries from our old and new customers!

Further information on the products presented here will be found at http://www.suntan.com.hk/pdf/Plastic-Film-Capacitors/TS08S.pdf

Now Suntan can support shorter lead time than other manufacturers on below series.

Mini Box Metalized Polyester Film Capacitor, only 5~6 weeks. Hot Offer Now!

General TS05 series: http://www.suntan.com.hk/pdf/Plastic-Film-Capacitors/TS05.pdf

Stacked TS05S series: http://www.suntan.com.hk/pdf/Plastic-Film-Capacitors/TS05S.pdf

Dipped Tantalum Capacitor TS19 series: http://www.suntan.com.hk/pdf/Tantalum-Capacitors/TS19.pdf

Besides, we now have strong support on our trimming potentiometer.

Trimming Potentiometer TSR series: http://www.suntan.com.hk/Trimming-Potentiometers/

If you have any requirement for these, please do check details with our experienced sales!

The multilayer ceramic capacitor has a many-layered dielectric. These capacitors are small in size, and have good temperature and frequency characteristics.

Square wave signals used in digital circuits can have a comparatively high frequency component included.This capacitor is used to bypass the high frequency to ground.

1.Please make sure the application and mounting conditions to which the capacitor will be exposed  are within the conditions specified in the catalog or alternate product specification (Referred as to specification here after).

2.Operating temperature and applied ripple current shall be within the specification.

The capacitor shall not be used in an ambient temperature which exceeds the operating temperature specified in the specification.

Do not apply excessive current which exceeds the allowable ripple current.

3. Appropriate capacitors which comply with the life requirement of the products should be selected when designing the circuit.

4. Aluminum electrolytic capacitors are polarized. Make sure that no reverse voltage or AC voltage is applied to the capacitors.  Please use bi-polar capacitors for a circuit that can possibly see reversed polarity.

Note: Even bi-polar capacitors can not be used for AC voltage application.

When DC voltage is applied, leakage current flows through a capacitor. The leakage current of aluminum electrolytic capacitors is larger than other types of capacitors; furthermore, the leakage current changes according to the temperature, applied voltage and application time.  If considering an equivalent circuit, the leakage current can be thought as the current flows through a resistance, which is connected in parallel to a capacitor. Leakage current becomes the power loss when capacitors are charged and self-discharge source when capacitors are discharged; therefore, it increases with error for the theoretical formulas.

The time constant in charge becomes lager than theoretical value and time constant in discharge becomes smaller than theoretical value. It is important to confirm that the capacitor meets the necessary requirements within the operating temperature range of the equipment, when using an aluminum electrolytic capacitor in a timing circuit.

An aluminum electrolytic capacitor consists of cathode aluminum foil, capacitor paper (electrolytic paper), electrolyte, and an aluminum oxide film, which acts as the dielectric, formed on the anode foil surface.

A very thin oxide film formed by electrolytic oxidation (formation) offers superior dielectric constant and has rectifying properties.  When in contact with an electrolyte, the oxide film possesses an excellent forward direction insulation property.  Together with magnified effective surface area attained by etching the foil, a high capacitance yet small sized capacitor is available.

As previously mentioned, an aluminum electrolytic capacitor is constructed by using two strips of aluminum foil (anode and cathode) with paper interleaved.  This foil and paper are then wound into an element and impregnated with electrolyte. The construction of an aluminum electrolytic capacitor is illustrated in Fig below.

The reliability of the solid tantalum capacitor is heavily influenced by environmental conditions such as temperature, humidity, shock, vibration, mechanical stresses, and electric stresses, including applied voltage, current, ripple current, transient current and voltage, and frequency. When using solid tantalum capacitors, therefore, provide enough margin so that the reliability of the capacitors is maintained. Voltage and temperature are important parameters when estimating the reliability.

Large capacitors are connected to the amplifier much the same way a battery is. This means that the capacitor's positive terminal is connected to the amplifier's positive terminal (which also means that it's connected to the battery's positive terminal). The same is true of the capacitor's negative terminal (the cap's negative terminal is connected to chassis ground with the amplifier's negative ground terminal). Like this...

Large capacitors are used as a sort of electrical shock absorber. As voltage starts to rise, the capacitor will absorb energy which will tend to keep the voltage from rising as quickly as it otherwise would. If the voltage starts to fall, the capacitor's stored energy will flow out of the capacitor to try to keep the voltage up. A capacitor's ability to absorb/release energy from/to external circuits depends on the capacitor's specs (capacitance, ESR, ESL...), the output impedance of the power source (alternator and power wire in this case) and the circuit's input impedance (into the amplifier's power supply).