Junction Field Effect Transistor

Its the presentation I prepaid on JFET it contains the construction and working ( at Vgs=0)of JFET.

1. Junction Field Effect Transistor (JFET) By – Ateeb Khan (S.Y. B.Tech)

2. Content Field Effect transistor (FET) Junction Field Effect Transistor ( JFET) Construction of JFET Working of JFET

3. Introduction The ordinary or bipolar transistor has two main disadvantage . • It has a low input impedance. • It has considerable noise level. To overcome this problem Field effect transistor (FET) is introduced because of its: • High input impedance • Low noise level than ordinary transistor

4. Field Effect Transistor is the voltage controlled device. FET

5. JFET   Junction Field Effect Transistor is a three terminal semiconductor device in which current conducted by one type of carrier i.e. by electron or hole. JFET:-

6. Construction   Source (S): The terminal through which the majority carriers enter into the channel, is called the source terminal . Drain (D): The terminal, through which the majority carriers leave from the channel, is called the drain terminal . Gate (G): There are two internally connected heavily doped impurity regions to create two P-N junctions. These impurity regions are called the gate terminal . Channel : The region between the source and drain, sandwiched between the two gates is called the channel .

7. Types Of JFET There are two types of JFET n-channel JFET P-channel JFET

8. Working JFET can worked in two conditions When V GS = 0 and V DS >0. When V GS < 0 and V DS >0

9. Mathematical model The current in N-JFET due to a small voltage V DS  (that is, in the linear ohmic region) is given by treating the channel as a rectangular bar of material of electrical conductivity. I D = bW . qN D µ n V DS L where I D  = drain–source current b  = channel thickness for a given gate voltage W  = channel width L  = channel length q  = electron charge = 1.6 x 10 −19  C μ n  = electron mobility N d  = n-type doping (donor) concentration. V P  = pinch-off voltage.

10. Linear region In Terms of I DSS

11. Channel Thickness Constant current region

12. Thank You