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Interesting facts and practical tricks with semiconductor diode

Interesting facts and practical tricks with semiconductor diode

In IC 7805, the three terminal voltage regulator IC, the output voltage that we get is fixed only to 5V strictly. This IC cannot be used to produce a voltage below 5V. But suppose this is our requirement. We want only 3V output voltage which should be regulated and using this IC only. Then it is very easy to use the IC together with just 3 silicon diodes in series with the output terminal of this IC. That is, connect 3–diodes in series with the output terminal and load resistor. The output voltage of the IC will be of course 5V. Now each of the diodes will drop around 0.7V across it. So the actual output voltage will be

5V – 2.1V = 2.9V which is approximately 3V.

Interesting puzzle of diodes

One interesting puzzle can be constructed using diodes. Take any semiconductor circuit working on DC power supply. The circuit has two terminals (+) and (–). Connect a bridge rectifier circuit across the two terminals such that the (+) and (–) terminals of bridge circuit will be connected to the respective terminals of the circuit. Take out two connecting wires from AC supply terminals of the bridge circuit.Now hide the bridge circuit inside a box with the working circuit itself. Only display the output result of the semiconductor working circuit.

  • Now tell your friend that he is given with a DC power supply and give him two terminals of the power supply as (+) and (–).
  • Tell him that the box contains one magical circuit which can work on both polarities of this DC power supply.
  • Also explain him that the semiconductor circuits work only on DC power supply. But this circuit is magical.
  • Now when your friend will try to connect the terminals of DC power supply to the circuit in BOTH WAYS, the circuit will work as it is, this is because there is our bridge rectifier circuit connected in between…!