This section is merely present to help you understand a few concepts which are necessary in order to grasp certain of the more technical aspects of this site. For those of us who may not be quite so well-informed regarding the relevant scientific areas, this section will provide explanations for one or two scientific subjects which one would need to understand some of the more technical issues surrounding the transistor.

Conventional Current

Current is the flow of charge. While electrons flow from the negative pole to positive pole, it is considered that the conventional current flows in the opposite direction, as far as an ordinary circuit is considered. Hence conventional current in an ordinary circuit always flows from the positive pole of a cell, through the circuit, to the negative pole.

In case of transistors, the charge, whether positive or negative, flowing towards the transistor is the conventional current

Alternating Current

There are two main types of electrical current: direct current, and alternating current (also known as fluctuating current). Whilst direct current flows continually in one direction, alternating current is the exact opposite. While it is also a continuous current, it is constantly reversing its direction. Alternating current can be displayed as a Sine curve, or wave, with a frequency of 50 Hz.

As alternating current comes in wave form, it also has the properties of frequency and amplitude. The frequency of a wave is the number of complete cycles it completes per second (measured in Hz), while amplitude is the maximum distance from the point of equilibrium. These two properties of the alternating current have an important part to play in amplification as they both have an affect on the properties of a sound wave - something which is very important in the use of the transistor in a radio. While the frequency affects the pitch, the amplitude is the important one, affecting the volume of the sound. For this reason when a transistor amplifies a sound, it is only the amplitude (volume) and not the frequency (pitch) which changes. In this way and the original sound gets louder and louder as the amplitude increases, but the quality or the pitch of the sound remains the same.

Ohm's Law

Current flows in an electric circuit in accordance with several definite laws. The basic law of current flow is Ohm's law, named for its discoverer, the German physicist Georg Ohm. This law applies mainly to metals. Ohm's law states that the amount of current flowing in a circuit is directly proportional to the potential difference across it and inversely proportional to the total resistance of the circuit. All of this is subject to a constant temperature. The law is usually expressed by the formula I = V/R, where I is the current in amperes, V is the potential difference in volts, and R is the resistance in ohms.

By now you may be wondering what this has to do with transistors, but in fact, has a major role to play in the world of transistors. According to Ohm's law, voltage will also vary according to resistance. This can be easily understood by merely looking at the formula. When switched around it reads: V=IR. Obviously then, the greater or smaller the resistance is, then the greater or smaller the potential difference will be. One of the major principles in the functioning of many of the world's the transistor depends on Ohm's law. This involves the use of transistors as amplifiers. When a current is passed from a circuit of low resistance to a circuit of high resistance, the voltage output will increase, because, as Ohm's law states: V=IR. And if the voltage output increases, it has been amplified!

Now that you understand Ohm's law, you should be able to understand the first principle for the functioning of transistor's in the Semiconductor Triodes section of this site.

Atomic Model and Bonding

All the elements on the periodic table, including silicon and germanium, are made up of minute, invisible particles, known as atoms. These atoms are neutral as a whole, therefore including equal amounts of positive protons and negative electrons. The protons together with the neutrons make up the nucleus, which constitutes the mass of the atom. The electrons are much lighter and constitute the atoms volume. Because they make up the atom's volume, they are free to move around the atom. In order to make it more convenient to study the atom, scientists have divided the atom into four orbits, or energy levels, in which the electrons move.

When atoms bond with other atoms to form molecules, it is the electrons in the outer orbit, or energy level, which do the actual bonding. These electrons are known as valence electrons. The elements of the periodic table, are arranged into groups I - VIII, according to the number of valence electrons in their outer orbit. The 2 semiconductor metals, silicon and germanium, are to be found in group four, obviously indicating four valence electrons.