Capacitors Blog

The T.C. of capacitance shall be within the limits shown in the table to the right. The T.C. shall be determined by measuring the capacitance (capacitor shall be set at approximately 75% of the guaranteed maximum capacitance) at +25, -55°C and either +85°C or +125°C,whichever is applicable to the respective style, at a frequency of 0.1 to 1 Megahertz. Each measurement shall be made after the capacitor has reached thermal stability.

Water in the electrolyte plays a big role. It increases conductivity thereby reducing the capacitor’s resistance, but it reduces the boiling point so it interferes with high temperature performance, and it reduces shelf life. A few percent of water is necessary because the electrolyte maintains the integrity of the aluminum oxide dielectric. When leakage current fows, water is broken into hydrogen and oxygen by hydrolysis, and the oxygen is bonded to the anode foil to heal leakage sites by growing more oxide. The hydrogen escapes by passing through the capacitor’s rubber seal.

One of the problems with electrolytic capacitors is that they have a limited frequency response. It is found that their ESR rises with frequency and this generally limits their use to frequencies below about 100 kHz. This is particularly true for large capacitors, and even the smaller electrolytic capacitors should not be relied upon at high frequencies. To gain exact details it is necessary to consult the manufacturers data for a given part.

This variant of the tantalum capacitor family is also known as the solid tantalum, and it is the variety that is most commonly used. Many millions of them are sued each day, and they can be found in many items of consumer and commercial electronic equipment.

The capacitor was developed by the Bell Telephone Laboratories by using a porous anode and then replacing the liquid electrolyte with a solid semiconductor. This overcome the problem od requiring a vent that is common to all other forms of electrolytic capacitor.

These capacitors are superior to electrolytic capacitors in many ways exhibiting excellent temperature and frequency characteristics. They are also smaller than their aluminium electrolytic counterparts.

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This is an effective resistance that is used to describe the resistive parts of the impedance of certain electronic components. The theoretical treatment of devices such as capacitors and inductors tends to assume they are ideal or "perfect" devices, contributing only capacitance or inductance to the circuit. However, all (non-superconducting) physical devices are constructed of materials with nonzero electrical resistance, which means that all real-world components contain some resistance in addition to their other properties. A low ESR capacitor typically has an ESR of 0.01 Ω. Low values are preferred for high-current, pulse applications. Low ESR capacitors have the capability to deliver huge currents into short circuits, which can be dangerous.

For capacitors, ESR takes into account the internal lead and plate resistances and other factors. An easy way to deal with these inherent resistances in circuit analysis is to express each real capacitor as a combination of an ideal component and a small resistor in series, the resistor having a value equal to the resistance of the physical device.

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 (field failure rate).

A Potentiometer with a power rating of (say) 0.5W will have a maximum voltage that can exist across the pot before the rating is exceeded.

All power ratings are with the entire resistance element in circuit, so maximum dissipation reduces as the resistance is reduced (assuming series or "two terminal" rheostat wiring).

Let's look at the 0.5W pot, and 10k is a good value to start with for explanation.
If the maximum dissipation is 0.5W and the resistance is 10k, then the maximum current that may flow through the entire resistance element is determined by ...

P = I² R ... therefore
I =P / R ... so I = 7mA

In fact, 7mA is the maximum current that can flow in any part of the resistance element, so if the 10k pot were set to a resistance of 1k, current is still 7mA, and maximum power is now only 50mW, and not the 500mW we had before.

Extremely low dissipation factor, higher dielectric strength than polycarbonate and polyester films, low moisture absorption, and high insulation resistance. May use plates of foil, metalized film, or a combination. Film is compatible with self-healing technology to improve reliability. Usable in high frequency applications and high frequency high power applications such as induction heating (often combined with water-cooling) due to very low dielectric losses. Larger value and higher voltage types from 1 to 100 μF at up to 440 V AC are used as run capacitors in some types of single phase electric motors.

Ceramic capacitors are suitable for moderately high-frequency work (into the high hundreds of megahertz range, or, with great care, into the low gigahertz range), as modern ceramic caps are fairly non-inductive compared to the other major classes of capacitors (film and electrolytic). Capacitor technologies with higher self-resonant frequencies tend to be expensive and esoteric (typically, mica or glass capacitors).

Sample self-resonant frequencies for one set of C0G and one set of X7R ceramic capacitors are:

Tantalum SMD capacitors are widely used to provide levels of capacitance that are higher than those that can be achieved when using ceramic capacitors. The capacitor technology that is used within SMD tantalum capacitors is based on the solid tantalum capacitor technology. This is robust and enables very small capacitors to be made.
For many years tantalum capacitors were used in SMD applications because electrolytic capacitors were not able to survive the high temperatures of the soldering process. Now that electrolytic capacitor technology has been developed to withstand the soldering process, these capacitors are now also widely used. Despite this, the other advantages of tantalum capacitors are employed in many circuits, and they are still used in vast quantities.
For Suntan TS20 SMD Tantalum Capacitor, It has the following Features:

• Molded case available in six case codes
• Compatible with all popular 'High Volume' automatic pick and equipment
• Optical character recognition qualified