Hello everyone, today we are going to conduct the p-n junction diode characteristics experiment. In this we are going to observe the forward bias characteristics as well as the reverse bias characteristics. This is the circuit diagram of forward bias.
This is the p-n junction diode. Okay, this is the diode. Okay, it is a diode. It is a diode having the two terminals.
It is a p-type and a n-type. It is an anode and it is a cathode. Okay, now here For this circuit diagram, for the diode we are connecting one resistor connected in series that is 1k ohm resistor.
And it is RPS positive and RPS negative. And this voltmeter is used to measure the voltage across this diode. And this ammeter is used to current passing through this diode.
We are using this ammeter. Now let's connect the circuit. Here this is the diode.
1k ohm second terminal is connected to diode P type here. As both are connected we should connect vertically only. Now RPS positive is connected to 1k ohm first terminal. Next RPS negative is connected to ground.
Next voltmeter, here if you see the diagram, voltmeter positive is connected to diode P type and voltmeter negative is connected to diode N type. okay here voltmeter positive connect here okay next voltmeter negative is connected to diode n type okay across this diode we are connecting one voltmeter okay next ammeter positive here ammeter positive is connected to diode n type here okay next this ammeter negative is connected to ground ammeter negative is connected to ground okay so if you see the junction point here this is one kilo ohm second terminal this diode p type and the multimeter positive three terminals are connected to junction point that's why here there are three terminals here one two three terminals are connected to a junction point if you see the ground terminals all rps negative and the ammeter negative is connected to ground these two terminals are connected to ground here instead of connecting these two terminals are connected to ground we can connect this rps negative we can connect directly to the ammeter negative we can we can connect in this way okay now if we vary the rps value here now i am increasing the rps value and we will see the voltmeter forward voltage and the forward current how we will get the values we will see here now i am increasing the rps value slowly up to we will get 0.1 volt in the voltmeter here the forward i am increasing the rps value and we are getting 0.1 volt forward voltage at 0.1 volt of the forward voltage we are getting the forward current is zero again slowly i am increasing the rps value okay so here at 0.2 volts at exactly at 0.2 volts we are getting the zero here and again if you increase the rps value further here at exactly 0.3 volts we are getting the forward current is zero only there is no conduction here If you increase the RPS value further here, here we are getting the 0.4 volts. At 0.4 volts, there is a slight decreasing, but here there is no change here, 0 milliamps only.
At 0.4 volts of the forward voltage, we are getting the 0 milliamps of forward current. Up to 0.4 volts, there is no conduction. At 0.5 volts, okay, if you increase the RPS further here, okay, you are getting 0.4 volts of RPS. 0.5 volts here there is a slight there is a slight increasing the ammeter value here at 0.5 volts of the forward voltage if you increase the rps value we will get here 0.5 volts at 0.5 volts of the forward voltage we are getting the 0.6 milliamps of current there is a slight increasing okay now at 0.6 volts okay at 0.6 volts we are getting around 3.5 milliamps of current we are getting forward current at 0.6 volts okay we are getting 3.6 milliamps okay now if you increase the current further here if you increase the rps further here we will get 0.7 okay for the if you increase the rps here we will get the 0.7 for the 0.7 volts we will get the current here we will take the maximum current here there are different currents we are getting but if you increase the rps further we are getting the different different of the a current here we will take the maximum current here okay we will take around 25 milliamps it is enough up to 25 milliamps of reading we can enough at 25 volts of the supply voltage 0.7 volts for the 0.7 volts we are getting the max 25.2 milliamps for the supply voltage is 25. From this we can say that up to 0.6 volt there is a slight increase in the current.
At 0.7 volts the current is increasing drastically in the forward bias. from this we can say that the cut-in voltage of the silicon this diode is a silicon diode for the silicon diode the cut-in voltage is 0.7 volts okay for the 0.7 volts the diode starts conducting cut-in voltage means the voltage where the diode starts conducting is called as a cut-in voltage. In the forward bias at exactly 0.7 volts the current is increasing drastically.
This is about the forward bias. If you see the whatever the values we got up to now if you note down these we are getting this is a supply voltage and it is a forward voltage it is a forward current. At 0.1 volts we are not getting any value. 0.2 volts also no value. 0.3 volts no value.
0.4 volts there is a slight increasing. At 0.5 volts also there is slight increasing the value. At 0.6 volts we are getting this 10.2 milliamps.
So you may get the nearby 10.2. It is not necessary to get exactly 10.2 you can you may get the nearby 10.2. So if you increase the supply voltage again we will get 0.7 volts.
At 0.7 volts the cut-in the forward current increases drastically. This current also you will get nearby this value. okay there is not necessary to get the exactly this value okay from this we can up if you increase the rps further here there is no increasing this voltage this 0.7 volts is the last for the pn junction diode okay so this is about the forward bias in the reverse bias just we will reverse the terminals here This circuit diagram for the reverse bias the negative terminal is connected to this p type and the positive terminal is connected to ground. Okay now if we reverse the terminals just reverse the terminals here and remove the this ammeter value and connect the this microamps value here because we use micro ammeter to measure the current the each and every connection is same just replace the milliamps meter by okay microamps meter because the in reverse by yarns we will get the very small currents okay that's why We will use the microamps in the forward bias we use milliamps in the reverse bias we use microamps the connections are as it is just reverse them RPS terminals if you reverse the RPS terminals we will get RPS negative RPS negative is connected to 1 kilo ohm first terminal here RPS negative is connected to 1 kilo ohm first terminal and RPS positive is connected to ground here. And connecting RPS positive is connected to ground.
Okay, this is the reverse bias connection. Now if we increase the rps value here slowly the each and every connection is same just we are replacing the rps terminals negative is connected to 1 kilo ohm first terminal and rps positive is connected to ground and we are replacing milli amps by micro amps. Now I am increasing the rps value here at 0.1 volt of the reverse voltage we are getting at 0.1 volt. we will get 0.1 volt microamps okay now at 0.2 volts of the reverse voltage we will get 0.2 microamps of the current we will get now if we increase the value further so like this if you increase we will take the 1 volt here if you take the 1 volt here for the 1 volt okay the reverse voltage we are taking 1 volt the reverse current also we are getting 1 micro amps next if you increase the rps further at 2 volts reverse voltage of 2 volts the reverse current we are getting 2 microamps only minus and if you take the voltage is 3 volts here if you take the voltage the micro amps current you are getting 3 microamps now If you take the voltage up to 4 volts here, if you take the reverse voltage, I am taking 4 volts.
If it is for 4 volts, the reverse current also you are getting the 4. We will get the linear characteristics here. If you take the 5 volts, you will get the 5. If you get the 6 volts, if you get the 6, if you take the 6 volts, okay, here. For the reverse voltage of the 6 volts, the reverse current is also same.
Like this, we will get the linear characteristics in the reverse bias. This is about the forward bias and reverse bias characteristics of the p-n junction diode. If you see the reverse bias characteristics, the table, this is the reverse bias table.
In the reverse bias, it is applied voltage and it is a reverse voltage and it is reverse current. All we will get the same here. In the p-n junction diode, we will get the linear characteristics, reverse bias.
Okay, now if you see the, sir, if you draw the graph for the forward bias and reverse bias, we will get the graph like this. Up to 0.7 volts, there is a small increase in the current. After 0.7 volts, the current increasing drastically. For the reverse bias, we will get the linear characteristics. for the forward bias and reverse bias.
This reverse bias characteristics we have to draw in the third quadrant as we get the negative values here. Okay. It is a minus 1, minus 1, minus 2, minus 2, minus 3, minus 3, minus 4, minus 4. Like this we will get the linear characteristics. This is about the forward and reverse bias characteristics of p-n junction diode.