Why cant a conductor be used for amplifying purpose.why is a semiconductor used?

Answer 1

In an Information Technology (IT) context, the signals that we want to amplify most often nowadays are carried by microwaves, light and 'regular electronics'. From the question, 'regular electronics' is presumed with frequencies in the radio to lower microwave range. This range includes electronic digital computers and most domestic electronics.

To amplify a signal one needs to switch or otherwise control a large current or voltage or 'other' with a small current or voltage or 'other'. Typically, human ingenuity has found many ways to do that.

Therefore, the answer is that semiconductors are not required for amplification of electrical signals. Conductors (in one way or another, though we should define our terms carefully) can often be used. The underlying truth is there are usually many factors that influence our choices of technologies. Obvious ones are that the technologies are very cheap, easy to produce, can be miniaturised, can work at high speed, use low power, are reliable and so on. Semiconductors meet all those requirements very well.

If you would like to consider an alternative, consider a thermionic valve such as the triode. The thermionic valves were the first widely-used electrical amplification devices. They are relatively simple to understand and they work extremely well. However, they are physically large, they generate a lot of heat, they cannot be miniaturised in any significant way, and they tend to have a short lifetime (compared with a transistor).

A limitation of semiconductors is that they break down if you use very high voltages or very large currents.

Consequently, thermionic valves are still used today for very high voltage and very high power applications.

If we assume that amplifiers are imperfect we might ask about the imperfections. Many audiophiles (lovers of music) insist that thermionic valve amplifiers sound much better than semiconductor amplifiers. Therefore, many guitar amplifiers and the top-of-the-range HiFi amplifiers tend to use thermionic valves.

If you would like a second example, consider any type of relay. It meets the requirement for an amplifier, though it is limited to the amplification of digital signals only.

Thermionic valves and many of the types of relays could be described as being made of conductors only. We use semiconductors (most of the time) for the amplification of electrical signals because they are very cheap, easy to produce, can be mass-produced and miniaturised, can work at relatively high speeds, use low power, are reliable and so on.

DonB