Tech blog Understand The Background Of Transistor Now

Understand The Background Of Transistor Now


What are the invention and innovations, which changed the world

It is not uncomplicated to say, which inventions have the most effective influence on modern life. Because the wide range of things we are using is not the result of any single discovery. But its a result of gradual inventions and improvements according to our requirements.

Firstly consider the categorization done by national geography for top 10 innovations.

  1. Printing press
  2. Lightbulb
  3. Aeroplane
  4. Personal computer
  5. Vaccines (immunity against disease)
  6. Automobile
  7. Clock
  8. Telephone
  9. Refrigeration
  10. Camera

Now let’s have a glance on some milestone modern day inventions.

  • The electric Dynamo -1831 (invented by Michael Faraday).
  • Plastic -1869 (by John Wesley Hyatt).
  • Telephone  -1876 (by Alexander Graham Bell).
  • Mobile phone  (by Martin Cooper an American engineer) by Motorola in 1970 but came in the market in 1983.
  • Light bulb -1879 (by Thomas Edison).
  • Transistor -1947

Here, we will be discussing about transistor, which is the only responsible for bringing up the computer from a fixed room to a table (as it successfully replaced the vacuum tube) and even making all electric appliances more advance and compact. Let’s discuss about it in details to understand its vital role in digitalization.

What is the transistor?

The transistor is a semiconductor device that regulates current and voltage flow and acts as a switch or gate for electric signals. It consists of three layers of semiconductor material each capable of carrying a current.

It was invented by three scientists at the Bell laboratories in 1947 and it rapidly replaced the vacuum tube as an electronic signal regulator. A transistor regulates current or voltage flow and acts as a switch or gate for electronic signals. A transistor consists of three layers of semiconductor materials and is capable of carrying a current. Semiconductor materials such as Germanium and silicon conducts electricity in a semi-enthusiastic way. Somewhere between a real conductor such as copper and an insulator like rubber and plastic.

How are transistors made?

Transistors are made from silicon a chemical element found in the sand which does not normally conduct electricity silicon is a semiconductor which means it’s really a conductor and insulator if you treat Silicon with impurities the process known as doping we can make it behave in a different way. If you dope Silicon with the chemical elements like Arsenic, Phosphorus or Antimony the Silicon they have extra electrons thus, some extra free electrons, that can carry an electric current. so electrons will flow out of it more naturally. Because electrons have a negative charge hence Silicon treated this way is called N-type. we can also dope silicon with other materials such as Boron gallium and Aluminium, they have less electron to fill its octet. hence, Silicon treated with this way has fewer of those free electrons so, the electrons in nearby materials will tend to flow into it. We call this sort of silicon P-type.

It’s important to note that neither N-type or P-type silicon is actually has a charge in itself, both are electrically neutral. It’s true that n-type Silicon has the extra free electron that increases its conductivity while P-type Silicon has fewer of those electrons which helps to increase its conductivity in the opposite way. In these cases, the extra connectivity comes from having added neutral and charged atoms as impurities to Silicon that was neutral to start with and we can’t create electrical charge out of thin air!

How does transistor work?

The semiconductor material is given special properties by a chemical process called doping. The doping results in a material that either adds extra electrons to the material which is then called n-type for the extra negative charge carriers or creates holes in the materials crystal structures which is called P-type. Because it results in more positive charge carriers. The transistors three-layer structure contains an n-type semiconductor layer sandwiched between p-type layers of PNP conjunction or P-type layer between conjunction layers and NPN configuration.

A small change in the current or voltage at the inner semiconductor layer which acts as the control electrode produces a large rapid change in the current passing through the entire component. The component can act as a switch opening and closing an electronic Gate many times per second. Today’s computers used circuit made with (complementary metal oxide semiconductors) CMOS technology used as a complementary transistor. Forget one with an n-type material the other with p-type material when one transistor is maintaining a logic state requires almost no power.

Transistors mainly work as

When Transistor work as a switch (source Wikipedia)

Transistors are commonly used in digital circuits as electronic switches which can be either in an “on” or “off” state, both for high-power applications such as switched-mode power supplies and for low-power applications such as logic gates. Important parameters for this application include the current switched, the voltage handled, and the switching speed, characterized by the rise and fall times.

In a grounded-emitter transistor circuit, such as the light-switch circuit shown, as the base voltage rises, the emitter and collector currents rise exponentially. The collector voltage drops because of reduced resistance from collector to emitter. If the voltage difference between the collector and emitter were zero (or near zero), the collector current would be limited only by the load resistance (light bulb) and the supply voltage. This is called saturation because current is flowing from collector to emitter freely. When saturated, the switch is said to be on.

Providing sufficient base drive current is a key problem in the use of bipolar transistors as switches. The transistor provides current gain, allowing a relatively large current in the collector to be switched by a much smaller current into the base terminal. The ratio of these currents varies depending on the type of transistor, and even for a particular type, varies depending on the collector current. In the example light-switch circuit shown, the resistor is chosen to provide enough base current to ensure the transistor will be saturated.

In a switching circuit, the idea is to simulate, as near as possible, the ideal switch having the properties of an open circuit when off, short circuit when on, and an instantaneous transition between the two states. Parameters are chosen such that the “off” output is limited to leakage currents too small to affect connected circuitry; the resistance of the transistor in the “on” state is too small to affect circuitry; and the transition between the two states is fast enough not to have a detrimental effect.

The transistor as an Amplifier

The common-emitter amplifier is designed so that a small change in voltage (Vin) changes the small current through the base of the transistor; the transistor’s current amplification combined with the properties of the circuit means that small swings in Vin produce large changes in Vout.

Various configurations of single transistor amplifier are possible, with some providing current gain, some voltage gain, and some both.

From mobile phones to televisions, vast numbers of products include amplifiers for sound reproduction, radio transmission, and signal processing. The first discrete-transistor audio amplifiers barely supplied a few hundred milliwatts, but power and audio fidelity gradually increased as better transistors became available and amplifier architecture evolved.

Modern transistor audio amplifiers of up to a few hundred watts are common and relatively inexpensive.

How they changed the world

Transistors have replaced the vacuum and following are the advantages it has over vacuum tube.

  • no cathode heater (which produces the characteristic orange glow of tubes), reducing power consumption, eliminating delay as tube heaters warm up, and immune from cathode poisoning and depletion;
  • very small size and weight, reducing equipment size;
  • large numbers of extremely small transistors can be manufactured as a single integrated circuit;
  • low operating voltages compatible with batteries of only a few cells;
  • circuits with greater energy efficiency are usually possible. For low-power applications (e.g., voltage amplification) in particular, energy consumption can be very much less than for tubes;
  • complementary devices available, providing design flexibility including complementary-symmetry circuits, not possible with vacuum tubes;
  • very low sensitivity to mechanical shock and vibration, providing physical ruggedness and virtually eliminating shock-induced spurious signals (e.g., microphonics in audio applications);
  • not susceptible to breakage of a glass envelope, leakage, outgassing, and other physical damage.



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