Photodiode

Photodiode technology developments came out of the basic developments of the PN junction diode that started in the 1940s in earnest. Applications for the use of the PN junction diode were found outside the basic use of rectifying signals. It was found that they could be used for many photonic applications - photodiodes, solar cells and light emission.
Photodiode technology was refined in the 1950s and in the latter part of that decade the PIN photodiode was developed. Light absorption in the wide depletion area of the PIN structure was first investigated in a paper published in 1959 by Gartner. Although silicon has been the favoured material for photodiodes, germanium can also be used, and its use was first demonstrated in 1962 by Riesz.
While PIN photodiode technology has been the most widely used format for diodes, other types including the avalanche diode were also demonstrated. The first step along the road was undertaken in 1953 by McAfee and McKay who first addressed the concept of avalanche multiplication and later work appeared on avalanche photodiodes in 1963 and the following years.
Another form of photodiode, named the Schottky photodiode has also been addressed. Some of the first research on point contact photodetectors appears to have been undertaken around 1962, and later diodes using evaporated metals films were also studied.

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Light Emitting Diode

Light emitting diodes, commonly called LEDs, are real unsung heroes in the electronics world. They do dozens of different jobs and are found in all kinds of devices. Among other things, they form numbers on digital clocks, transmit information from remote controls, light up watches and tell you when your appliances are turned on. Collected together, they can form images on a jumbo television screen or illuminate a traffic light.
Basically, LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don't have a filament that will burn out, and they don't get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor. The lifespan of an LED surpasses the short life of an incandescent bulb by thousands of hours. Tiny LEDs are already replacing the tubes that light up LCD HDTVs to make dramatically thinner televisions.

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Laser diode

Laser diode technology is in widespread use today in many areas of the electronics industry.
Laser diode technology is now well established, with laser diodes providing a cost effective and reliable means of developing laser light.
With laser diodes being lending themselves to use in many areas of electronics from CD, DVD and other forms of data storage through to telecommunications links, laser diode technology offers a very convenient means of developing coherent light.

Laser diode overview

Laser diodes are used in all areas of electronics from domestic equipment, through commercial applications to hash industrial environments. In all these applications laser diodes are able to provide a cost effective solution while being rugged and reliable and offering a high level of performance.

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Silver mica capacitor

Silver mica capacitors have been widely used as high performance capacitors over the years. Although silver mica capacitors are not as widely used, these days, nevertheless they are still available and used in a variety of applications where their particular properties are needed.

Silver mica capacitors are able to provide very high levels of accuracy, stability and low loss. As a result silver mica capacitors found many uses in radio frequency applications, particular for oscillator and filter circuits where their stability, accuracy and low loss (leading to high Q) were needed. Although not as widely used these days, they can still be obtained and are used where stability of value is of the utmost importance and where low loss is required.

Two main reason for the decline in the use of silver mica capacitors is their size, resulting from the materials used and their construction. The cost of silver mica capacitors is higher than many other types that can often be used these days.

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Tantalum capacitor

Tantalum capacitors are widely used in electronics design these days. Tantalum capacitors offer a form of capacitor that provides a very high capacity density. As a result this form of capacitor has found widespread use in many areas of electronics. In view of its size and the attainable levels of capacitance, these capacitors are widely used in many mass produced items of electronics equipment.

The tantalum capacitor is similar to the electrolytic capacitor, but using tantalum within the construction of the capacitor it is able to offer extremely high levels of capacitance for any given volume. As such tantalum capacitors are widely used in electronics equipment where there is a need for small size and a high level of capacitance. In view of its advantages, the tantalum capacitor is used in large volumes within the electronics manufacturing industry.

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Electrolytic capacitor

Today electrolytic capacitors or as they are more correctly termed, aluminium electrolytic capacitors are used in huge quantities. They are very cost effective and able to provide a larger capacitance per volume than other types of capacitor. This gives them very many uses in circuits where high currents or low frequencies are involved. Aluminium electrolytic capacitors are typically used most in applications such as audio amplifiers of all types (hi-fi to mobile phones) and in power supply circuits.

Like any other capacitor, it is necessary to understand the advantages and limitations of these capacitors to enable them to be used most effectively.

Electrolytic capacitor development

The electrolytic capacitor has been in use for many years. Its history can be traced back to the very early days or radio around the time when the first broadcasts of entertainment were being made. At the time, valve wireless sets were very expensive, and they had to run from batteries. However with the development of the indirectly heated valve or vacuum tube it became possible to use AC mains power. While it was fine for the heaters to run from an AC supply, the anode supply needed to be rectified and smoothed to prevent mains hum appearing on the audio. In order to be able to use a capacitor that was not too large Julius Lilienfield who was heavily involved in developing wireless sets for domestic use was able to develop the electrolytic capacitor, allowing a component with sufficiently high capacitance but reasonable size to be used in the wireless sets of the day.

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Ceramic capacitor

Ceramic capacitors are one of the most widely used forms of capacitor used in electronics equipment these days. Ceramic capacitors have also been used for many years, being found in valve or tube circuits dating from the 1930s.

Today ceramic capacitors area available in a variety of formats ranging from leaded components to surface mount technology, SMT varieties. As leaded versions disc ceramic capacitors are widely available, and as SMT devices, ceramic capacitors are available in all the common formats. As such these ceramic capacitors are used in virtually every type of electronics equipment.

The actual performance of the ceramic capacitors is highly dependent upon the dielectric used. Using modern dielectrics, very high values are available, but it is also necessary to check parameters such as the temperature coefficient and tolerance. Different levels of performance are often governed by the dielectric used, and therefore it is necessary to choose the type of dielectric in the ceramic capacitor.

Ceramic capacitors range in value from figures as low as a few picofarads to around 0.1 microfarads. In view of the wide range and suitability for RF applications they are used for coupling and decoupling applications in particular. Here they are by far the most commonly used type being cheap and reliable and the loss factor is particularly low although this is dependent on the exact dielectric in use.

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capacitor

A capacitor (formerly known as condenser) is a passive two-terminal electrical componentused to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric (insulator); for example, one common construction consists of metal foils separated by a thin layer of insulating film. Capacitors are widely used as parts of electrical circuits in many common electrical devices.

When there is a potential difference (voltage) across the conductors, a static electric fielddevelops across the dielectric, causing positive charge to collect on one plate and negative charge on the other plate. Energy is stored in the electrostatic field. An ideal capacitor is characterized by a single constant value, capacitance, measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them.

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