N channel j-fet

SMART WORK FOR GREAT SUCCESS.....

1. n- Channel j- fet Presented By Shirisha Reddymalla..

2. N-channel j- fet Here we have 3-components 1. SOURCE 2. DRAIN 3. GATE SOURCE : where majority charge carries entires the substrate called as source .

3. N-channel j- fet DRAIN : The terminal where the majority charge carries leave the path called as Drain. GATE: On both sides of the n-type substrates heavily doped p+ region or acceptor ions have been formed by alloying or diffusion .this impurity region is called as GATE. CHANNEL: The region of the N-type material between 2-gate region the channel. The channel is the path through which the majority carriers move from source to drain

4. Fet operation V ds is + ve in order to move electron from source to drain At the drain the junction is reverse bised compared to source The widing of depletion width is by 1)conducting to the + ve voltage to the n-type material Connecting + ve voltage to the p-type (at the gate ) so the gate is reverse bised w.r.t source as V gs increases negately .The width of the depletion layer increases the channel gets decreases

5. Conditions in j- fet Case1: V GS =0 1) V gs increases then depletetion region at drain increase and I d increases 2) At a particular point the two layers will touch each other then that point is called as ‘‘ pinch off point ’’. 3) At a particular voltage the two depletion width touch each other then that point is called as ‘‘ pinch off voltage ’’. 4) After pinch off point the V GS =0 or V GS =+ ve then I D is constant.

6. J- fet CASE:2 1)V GS negatively increases then.. Depletion width increases so that channel width decreases width. For V DS constant as V GS negatively increases the channel width decreases.

7. Characteristics or drain characteristics Here we have 3 regions Ohmic region saturation Cut off region

8. OHMIC REGION V DS >0 and V DS < V GS –V P this is called as ohmic region There is no pinch of the channel here When V GS increases negatively then the channel conductance decreases therefore resistance increases So the J-FET can be used as a voltage control resistor I D =f(V DS ) As V DS varies therefore I D is also varies The resistor in the ohmic region is typically varies from 100 ohms to 10K ohms

9. Saturation region V DS > V GS – v p I D is independent of V DS I D is dependent of V GS I D =f(V GS ) I D =I DSS (1- V GS /V P ) ²

10. CUT -OFF |V GS |> | V P | implies I D =0 For the JFET to work as a amplifier it is to be operated in “ saturation region ”. Output current depends on input voltage. Hence it is called as Trans Conductance Device.