00:01
Hello students for the first part of the question we are going to discuss the difference between collector characteristics of bjt and the drain characteristics of jfet.
00:15
First we should know that the bipolar junction transistor that is bjp is a current control device current control device whereas the jfet is a voltage control device junction field effect transistor is a voltage controlled device.
00:45
Now coming to the output current that is the collector current of here the collector current of bjp is controlled by controlled by base current base current i b.
01:08
In case of jfet the output current that is the drain current is controlled by controlled by input voltage input voltage which is the gate source voltage vgs.
01:32
Here the bjt has lower input impedance lower input impedance ri whereas jfet has higher input impedance.
01:47
Bjt has higher transconductance it has high transconductance when compared to jfet which has lower transconductance.
02:11
So these are the main difference between the output characteristics of bjt and the drain characteristics of jfet.
02:20
For the second part of the question the reason why the ig is that is the gate current is effectively is zero amperes for jfet transistors because in jfet transistors jfet gate is reverse biased gate is reverse biased which means that the gate source junction behaves like reverse biased diode which implies gate source junction behaves like reverse biased diode.
03:13
So in this condition ig is that is the gate current is very small that is approximately equal to zero due to the minority carrier flow due to minority carrier flow.
03:38
So it is as it is very small it is considered to be zero for jfet...
