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What is a transistor?

History of Transistors


1.Transistor was born in 1948 at the Bell Telephone Laboratories, USA.

The invention of the transistor that gave an unprecedented shock to the electronics industry at that time was made in the year 1948. That truly was the beginning of the current age of electronics. Thereafter, there have been extremely fast advances in electronics technology which includes computer technology as well. When we think of the contribution that has made our life so rich as it is today, it is natural that the inventors of the transistor, the three physicists, W. Shockley, J. Bardeen, and W. Brattain were awarded the Nobel prize. On wonders whether there will ever be another invention that can match the invention of the transistor. In any case, it is obvious that the transistor has had a very large impact indeed on the present state of affairs.

2.From Germanium to Silicon.

Initially, transistors were being manufactured using a semiconductor material called germanium. However, since germanium had the drawback that it broke down at a temperature of about 180.

3.The functions of a transistor are "Amplification" and "Switching".

Take for example a radio. The variations in the extremely weak signals coming through the atmosphere are magnified and output via a speaker. This function is carried out by the amplification operation of the transistor. Without changing the waveform of the input signal, only the voltage or the current of the signal is enlarged. While this is the case of analog signals, in the case of digital signals used in computers, etc., the transistor plays the role of a switch changing the state between 0 and 1. Even ICs and LSIs are basically collections of transistors, and the basis of their operation is still this amplification operation of transistors.

4.Resistors and transistors on single chip.

Conventionally, discrete resistors and transistors were being mounted on the same printed circuit board. Considering this, a transistor chip with built-in resistors was developed as a digital transistor.
The merits of a digital transistor are:
1. Reduction in the area required for mounting the components on the printed circuit board.
2. Reduction in the time required for mounting the components.
3. Reduction in the number of components.

Resistors and transistors on single chip

Digital transistors are covered by one of ROHM's exclusive patents.
Transistors with built-in resistors were developed by ROHM for the first time in the world and have been awarded the patent rights.

5.The base is like the cock of a water line, the emitter is the piping, and the collector is the tap.

The base is like the cock of a water line, the emitter is the piping, and the collector is the tap. The operation of a transistor can be compared to that of a water tap. A transistor has three legs. These are called the emitter, the base, and the collector, respectively. The base corresponds to the cock of a water line, the collector to the tap, and the emitter to the piping of water. By controlling the cock with a small force (corresponding to the input signal of the base), it is possible to control a large water flow rate out of the tap (corresponding to the current flowing through the collector). This is an easy way to understand the operation of a transistor.

6.Let us now give the proper explanation.

Let us now give a more correct and detailed explanation of the principle of amplification operation of the transistor using Fig. 1 and Fig. 2. A current (Ic) flows through the collector that is equal to the product of hfe (*1) and the current through the base (IB) which is proportional to the base-emitter voltage (VBE) consisting of the input voltage e and the bias voltage E1. When this collector current Ic flows through the resistor RL, a voltage equal to Ic × RL appears across the resistor RL. Effectively, the input voltage e appears at the output after being converted (amplified) into a voltage of IcRL.

(*1) hfe: DC Current amplification factor of the transistor.

Fig. 1 Fig. 2