The Fundamental Basis of Modern Electronics

A small amount of energy creating an effect on a larger amount of energy.

This basic principle, has advanced human society for millennia.

History is full of examples.

An ancient farmer controlling  a large beast, like a horse or an ox to plough a field. This marked the begining of the farming revolution.

One man opening and closing a sluce gate to control the power of a mighty water wheel. This Marked the begining of the industrial Revolution.

This basic principle,  has also driven the advancement of electronic technology for the past 100 years.

What is electricity?

An ANALOGY is probably the best way to understand electricity.

Imagine a white water river, the water rushes past creating splashes, imagine the splashes are electrical sparks. The speed of the river rushing past is voltage.
Now imagine widening the banks of the river. The white water disappears, and the rush of the water slows. In electrical terms the width of the river is called current or ampage.
Even though we have altered the width and speed of the river the same amount of water passes by.
In electronics we can change voltage for ampage or ampage for voltage using a simple device called a transformer.
I will come back to this river analogy later.

If I was to cut a wire running to a light bulb, the light would go out.
If I pushed the wire back together the light would come on again.
I have created a mechanical switch.
How could I create a non mechanical switch, that also controlled the brightness of the light bulb?

Some people will remember valve TVs and valve Radios. You would switch them on. A dim orange glow would eminate from the back of the set. The room would fill with the smell of scorched dust and hot bakelite.
Then about a minute later, the device would slowly and begrudgingly come to life.

Valves were the first technology to use the basic principle of a small amount of electricity having an effect on a large amount of electricity.


A Triode valve is a simple sealed glass tube with the air extracted.
Inside the tube there is a tungsten metal heating element. This element creates electrons.
Imagine electrons as small metal ball bearings, they appear inside the glass tube from nowhere when the element is heated.
Now at the bottom of the valve is the live wire that I cut to make a mechanical switch. At the top of the valve is the other end of the wire that runs to the light bulb. The electrons or ball bearings now carry the electricity from the live wire at the bottom of the valve to the wire at the top. This creates a connection and the light bulb comes on.

Now we need to put another piece of wire in the middle of the glass tube. If we apply a small voltage to this third wire,  the electrons inside the valve will be attracted or repelled. Depending if we apply a negative or positive charge to it.
It is very similar to how two magnets can repel or attract.
By adjusting the voltage applied to this third wire we can control how many electrons make the arduous journey from the bottom to the top of the tube. We now have control over the on/ off status of the bulb and we can also control the brightness.

This is called Amplification or Modulation.
We can now connect this amplifier valve to a low voltage microphone and a high voltage speaker.
We can transmit, recieve and modulate a radio signal.
Or we could just use the valve to control an on /off state thereby creating a one bit binary code.  We could use eight valves together and create one binary byte. The basis of or modern computer systems.

In the 1970s valves were replaced by silicon transistors. A good analogy for silicon is a chocolate aero bar. It is full of holes and no electrical current can pass through these holes. However if we apply a small charge to the side of the silicon, the holes fill with electrons and current can pass freely. Triode valves and silicon transistors work on the same basic principle. There is however one important difference. Valves modulate voltage and silicon transistors modulate ampage.

So today rather than modulating the speed of the river we modulate the width of the river.


Paul Fear



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