Mica Capacitor

 
Mica Capacitor

What are mica capacitors? Mica is a group of natural minerals. Silver mica capacitors are capacitors which use mica as the dielectric. There are two types of mica capacitors: clamped mica capacitors and silver mica capacitors. Clamped mica capacitors are now considered obsolete due to their inferior characteristics. Silver mica capacitors are used instead. They are made by sandwiching mica sheets coated with metal on both sides. This assembly is then encased in epoxy in order to protect it from the environment. Mica capacitors are generally used when the design calls for stable, reliable capacitors of relatively small values. They are low-loss capacitors, which allow them to be used at high frequencies, and their value does not change much over time. Mica minerals are very stable electrically, chemically and mechanically. Because of its specific crystalline structure binding, it has a typical layered structure. This makes it possible to manufacture thin sheets in the order of 0.025-0.125 mm. The most commonly used are muscovite and phlogopite mica. The first has better electrical properties, while the second has a higher temperature resistance. Mica is delved in India, Central Africa and South America. The high variation in raw material composition leads to high cost needed for inspection and sorting. Mica doesn’t react with most acids, water, oil and solvents. Mica capacitor definition Silver mica capacitors use mica as the dielectric. They have great high-frequency properties due to low resistive and inductive losses, and are very stable over time. Characteristics Precision and tolerances The minimum tolerance for silver mica capacitor values can be as low as ±1%. This is much better than practically all other types of capacitors. In comparison, certain ceramic capacitors can have tolerances of up to ±20%. Stability Mica capacitors are very stable and very accurate. Their capacitance changes little over [… read more]

Polymer Capacitor

 

What are polymer capacitors? Polymer capacitors are capacitors which use conductive polymers as the electrolyte. They use solid polymer electrolytes instead of liquid or gel electrolytes that are found in ordinary electrolytic capacitors. By using solid electrolyte, the electrolyte drying is completely avoided. Electrolyte drying is one the factors that limit the lifetime of ordinary electrolytic capacitors. There are several types of polymer capacitors, including aluminium polymer capacitors, polymerized organic semiconductors and conductive polymer capacitors. In most cases, polymer capacitors can be used as direct replacements for electrolytic capacitors, as long as the maximum rated voltage is not exceeded. The maximum rated voltage of solid polymer capacitors is lower than the maximum voltage of classical electrolytic capacitors: usually up to 35 volts, although some polymer capacitors are made with maximum operating voltages of up to 100 volts DC. Polymer capacitors have a number of qualities superior to ordinary electrolyte capacitors: longer lifetime, higher maximum working temperature, better stability, lower equivalent series resistance (ESR) and a much safer failure mode. These qualities come at a price of lower maximum voltage rating and a narrower capacitance range, as well as a higher cost compared to wet electrolyte capacitors. This type of capacitor is not that new: production started in the 1980s and since then, they have been used in many applications including server motherboards and computer graphic accelerator cards. Polymer capacitor definition A polymer capacitor is a capacitor which uses solid polymers as the electrolyte. They have a number of superior qualities including a safer failure mode, lower losses and a longer lifetime than electrolytic capacitors. Characteristics Equivalent series resistance Compared to ordinary electrolytic capacitors, polymer capacitors have a lower equivalent series resistance. This allows polymer capacitors to withstand higher ripple currents during normal operation. A ripple current is the AC component [… read more]

Supercapacitor

 

What are supercapacitors? Supercapacitors are electronic devices which are used to store extremely large amounts of electrical charge. They are also known as double-layer capacitors or ultracapacitors. Instead of using a conventional dielectric, supercapacitors use two mechanisms to store electrical energy: double-layer capacitance and pseudocapacitance. Double layer capacitance is electrostatic in origin, while pseudocapacitance is electrochemical, which means that supercapacitors combine the workings of normal capacitors with the workings of an ordinary battery. Capacitances achieved using this technology can be as high as 12000 F. In comparison, the self-capacitance of the entire planet Earth is only about 710 µF, more than 15 million times less than the capacitance of a supercapacitor. While an ordinary electrostatic capacitor may have a high maximum operating voltage, the typical maximum charge voltage of a supercapacitor lies between 2.5 and 2.7 volts. Supercapacitors are polar devices, meaning they have to be connected to the circuit the right way, just like electrolyte capacitors. The electrical properties of these devices, especially their fast charge and discharge times, are very interesting for some applications, where supercapacitors may completely replace batteries. Supercapacitor definition A supercapacitor is a specially designed capacitor which has a very large capacitance. Supercapacitors combine the properties of capacitors and batteries into one device. Characteristics Charge time Supercapacitors have charge and discharge times comparable to those of ordinary capacitors. It is possible to achieve high charge and discharge currents due to their low internal resistance. Batteries usually take up to several hours to reach a fully charged state – a good example is a cell phone battery, while supercapacitors can be brought to the same charge state in less than two minutes. Specific power The specific power of a battery or supercapacitor is a measure used to compare different technologies in terms of maximum power output [… read more]