1 JFET Bollen

2 AGENDA Bollen JFET Overview JFET vs BJT Physical structure Working Input parameters DC formula Output parameters Transconductance Ac parameters Simulatioin parameters micro cap JFET Fixed bias Self bias Voltage divider bias MOSTFET Component DC ac

3 J-FET Bollen FET = Field Effect Transistor N-channel or P-channel

4 J-FET, OVERVIEW Bollen

5 JFET vs BJT Bollen

6 J-FET vs BJT Bollen

7 Physical structure Bollen There is one PN junction from gate to channel used in REVERSE

8 JFET working Bollen

9 JFET working Bollen

10 JFET input parameters Bollen Vp and Idss In data sheet p = pinch-off dss = drain source shorted or saturated = maximum current

11 JFET DC formula Bollen Solve with abc formula

12 JFET Output parameters Bollen Uds Up = saturated region

13 JFET Bollen JFET is not often used in the ohmic (triode) region If so it is used as an variable resistor

14 JFET output Bollen

15 JFET output Bollen

16 JFET transconductance Bollen

17 JFET transconductance Bollen

18 JFET ac parameters Bollen

19 JFET simulation parameters micro cap Bollen VTOThreshold voltage BETATransconductance parameter

20 JFET fixed bias Bollen Steady Ugs, no variation possible, so we make the same effect with resistors. U = I. R Now we can vary around the bias point

21 JFET self bias Bollen Ug = 0 volt, NO gate current Ugs = Ug – Us = 0 – Ids.Rs Rin = 1 Meg Ohm

22 JFET self bias Bollen Varying Rs = varying the Q-point = operating point

23 JFET voltage divider bias Bollen Ug  0 volt Ugs = Ug – Us = Vg – Ids.Rs, bias is made at GATE and SOURCE

24 MOSFET Bollen Metal Oxide Silicium Field Effect Transistor

25 MOSFET Bollen

26 MOSFET Bollen

27 MOSFET dc Bollen

28 MOSFET ac Bollen