BRACAU 27 BLOG'S

Theory: A diode is made up of semiconductor material usually silicon. A cathode and anode are adjacent to one another having opposite polarities. A depletion region is formed which has neither holes nor electrons. A positive voltage at anode terminal makes the depletion region small and current flow & a negative voltage at cathode makes it large and prevents the current flow.

A modern semiconductor diode is made of a crystal of semiconductor like silicon that has impurities added to it to create a region on one side that contains negative charge carriers (electrons), called n-type semiconductor, and a region on the other side that contains positive charge carriers (holes), called p-type semiconductor. The diode's terminals are attached to each of these regions. The boundary within the crystal between these two regions, called a PN junction, is where the action of the diode takes place. The crystal conducts conventional current in a direction from the p-type side (called the anode) to the n-type side (called the cathode), but not in the opposite direction.

I connected the circuit as shown in fig. I then plotted forward characteristic of diode and connected the p-type end to the positive sliding contact of potential divider R, through an AVO meter and resistance R₂

A resistance of order 100Ω is used to have a forward control on forward current as it is a very resistance parameter of forward voltage.

I connected the n-type end to negative of potential divider. A voltage ranging 0.3volts is connected to read the applied voltage.

I plugged in the key and set the AVO meter ranging 0-10 mA.

Start increasing the voltage and corresponding current at each step until it attains high specific value.

I plotted graph for forward voltage against forward current to obtain forward characteristic of diode.

After that I connected up the circuit as shown. Replace the battery by regulating power supply of 0-250 volts and voltmeter by 100 volts and connect n-type side of diode to positive side to negative terminal of power supply.

I plugged in the key and set in the AVO meter of range 0.25µA.

Now increasing the voltage in regular steps if some specific range comes note the corresponding current. Plotted the graph of reverse voltage and reverse current to obtain reverse characteristic of diode.