Diodes Questions and Answers for Viva

Answer-1: Insulator: - Insulator is a material which does not allow to flow of current trough itself is called insulator. Example: - wood, glass etc.
Conductor: - Metal is a material which allow to flow of current trough itself is called Conductor. Example: - Aluminum, Steel etc.
Semiconductor: - a Semiconductor is a material which has the resistivity in between semiconductor and insulator. Example: - Ge, Si, and C etc.

Answer-2: Solid state electronics arises from the unique properties of silicon and germanium, each of which has four valence electrons and which form crystal lattices in which substituted atoms (dopants) can dramatically change the electrical properties.

Answer-3: In solid state electronics, either pure silicon or germanium may be used as the intrinsic semiconductor which forms the starting point for fabrication. Each has four valence electrons, but germanium will at a given temperature have more free electrons and a higher conductivity. Silicon is by far the more widely used semiconductor for electronics, partly because it can be used at much higher temperatures than germanium. For silicon diodes, the built-in potential is approximately 0.7 V and 0.3 V for Germanium

Answer-4: when a p-type semiconductor is joint with an n-type semiconductor through VLSI technology then the resulting device is called pn junction diode. Diode is an electronics component having two terminals, cathode &anode, having non-linear characteristic end allowing the flow current in only 1 direction. The semiconductor diode is formed by forming a junction between P-type & other N-type of semiconductor. Diodes can have more complicated behavior than this simple on-off action.

Answer-5: Forward biased: - when p type semiconductor is connected to the +ve terminal of the battery and n type material is connected to the ?ve terminal of the battery then diode is called forward biased. At this condition, if the applied voltage is greater than the barrier potential of the diode, it starts conduction. After the diode is arrived in the conduction mode, the drop across it remains at 0.7 V. After the conduction starts, if the voltage is increased further, current trough it increases linearly with voltage.

Answer-6: Reverse biased: - when p type semiconductor is connected to the -ve terminal of the battery and n type material is connected to the +ve terminal of the battery then diode is called Reverse biased. Here there is no conduction at lower voltage values. If we increase the voltage value further, it is observed that at a voltage the current sharply increases due to the breakdown of the P-N junction.

Answer-7: Knee voltage is defined as the forward voltage at which barrier is removes and current through the junction starts increasing rapidly. Breakdown voltage is defined as the reverse voltage at which barrier is removed and inverse current through the junction starts increasing rapidly. It can be damages the diode.

Answer-8: A semiconductor diode?s behavior in a circuit is given by its current?voltage characteristic, or I?V graph .The shape of the curve is determined by the transport of charge carriers through the so-called depletion layer. In forward biasing after knee voltage current increase sharply and in reverse biasing small leakage current flow and after reverse breakdown voltage sharply inverse current will flow.

Answer-9: To check an ordinary silicon diode using a digital multimeter. Connect the positive lead of multimeter to the anode and negative lead to cathode of the diode. If multimeter displays a voltage between 0.6 to 0.7, we can assume that the diode is healthy. This is the test for checking the forward conduction mode of diode. Now connect the positive lead of multimeter to the cathode and negative lead to the anode.

Answer-10: For testing Germanium diodes, the procedure is same but the display will be between 0.25 to 0.3 V to indicate a healthy condition in the forward biased mode. The potential barrier for Germanium diode is between 0.25 and 0.3V.When reverse biased the multimeter will show an infinite reading (over range) indicate healthy condition.