Science & Technology in Action

15th Edition

Digital Electronics

Boston Scientific

Physics
Technology
Jnr Science Cert
This lesson summarises the development of electronics from the invention of the vacuum tube to single transistorised integrated circuits. Over the last twenty years or so inexpensive single chip computers have come on the market, often costing just a few euro. They can be programmed and used as microcontrollers in consumer products such as washing machines and motor cars.

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Lesson excerpt

Electricity

William Gilbert (1544 – 1603) is generally regarded as the father of electrical engineering or the study of electricity and magnetism. He was the inventor of the electroscope which he used to study what is now called ‘static electricity’. In 1600 he published a book (De magnete) in which he described his findings. The study of electricity and magnetism really took off following the invention of the electric battery in 1800 by Volta (1745 – 1827). The battery could produce a continuous fl ow of electric charge, or what we now call an electric current. It was quickly discovered that an electric current could produce a heating effect and a chemical effect (e.g. electrolysis). In 1820 the magnetic effect of electric current was discovered. By the end of the 19th century all sorts of electrical devices were in widespread use: telegraph, lights, heaters, cookers and motors. In the 1890s electric trams began to replace the horse-drawn trams in Dublin.

What is electronics?

The invention in 1904 of the so-called ‘vacuum tube’ is generally taken as the beginning of electronics. The vacuum tube could conduct electricity in one direction — it was what we now call a ‘diode’. Because of this effect the vacuum tube diodes were also known as ‘valves’. By 1906 other types of valve (such as triode and pentode) that could be used as amplifiers were also developed. These are regarded as active components in contrast to switches, lamps and electromagnets which are regarded as ‘passive’ components. Radio transmissions began in the 1920s although few homes had a radio receiver. In the US commercial television transmissions started in the 1940s. Since the 1950s vacuum tubes have been largely replaced by solidstate semiconductor devices such as transistors. These are smaller, cheaper and more reliable than vacuum tubes and require much less electrical power. Portable transistor radios and tape recorders became commonplace in the 1960s. Although the distinction between electrical and electronic devices is not entirely clear cut, today electronics generally involves the use of semiconductors.

True or False?

  1. The vacuum tube diode was invented in 1904. true
  2. The production of portable electronic equipment was facilitated by the invention of the transistor in 1947. true
  3. A microphone produces a digital electronic signal. false
  4. Logic gates are the building block of digital computers. true
  5. An analogue signal can be digitised by sampling it rapidly and assigning discrete values to each sample. true
  6. An integrate circuit is made by connecting many discrete components to form a single circuit. false
  7. Single chip computers were invented in the 1950s. false
  8. The first microprocessor chip had over 1000 transistors. true
  9. The resolution of a digital signal depends on the number of bits assigned to the sampled values. true
  10. Single chip microcontrollers are widely used in medicine. true
  11. Today’s motor cars may have thirty or more microprocessors to monitor such things as engine ignition, emergency braking, tyre pressure and internal environment. true

Glossary of terms

amplifier
a device that boosts the power of a varying signal
analogue
an electrical signal whose amplitude or frequency is a function of the variable being represented; e.g. the voltage produced by a microphone is proportional to the variation in the pressure of the sound wave it detects
defibrillation
a treatment (usually electrical) to restore the normal rhythm of the heart
electric battery
a chemical cell that produces a steady electric current
electric charge
Electric charge is a fundamental property of certain subatomic particles such as electrons and protons; there are two type, called positive and negative. Charged objects generally have a excess or deficiency of electrons.
electronics
study of electrical devices that use active components - typically transistors
electrolysis
the decomposition of a compound by passing an electric current through it; this is an example of the conversion of electrical energy to chemical energy
electroscope
a device for detecting electric charge; it was invented in the mid 18th century
ICD
Implantable Cardioverter Defibrillator
microphone
a device that converts sound energy to electrical energy
microprocessor
the chip at the heart of the computer; the main processing device
sampled
repeatedly measured
static electricity
electricity phenomena associated with non-moving charges
semiconductor
A material with electrical resistance between those of conductors and insulators.
silicon
a grey shiny semi-metallic element
speaker
(or loudspeaker); a device that converts electrical energy to sound
truth table
logic table that depicts a circuits output response to the various combinations of the logic levels at its inputs
electric current
a flow of electric charge. This can be a flow of electrons (in metals) or ions (in the case of gases and ionic solutions).