1. Field Effect Transistors Next to the bipolar device that has been studied thus far the Field Effect Transistor is very common in electronic circuitry, though different you will no doubt observe it is similar in many ways. Features

2. Field Effect Transistors FET ; Used; In Switching Circuits, Amplifiers, & Digital circuits. Advantages; 1. High Input Impedance. 2. Low Noise Figure 3. Operates w/ a small voltage @ the Gate, Controls 100% of the current from Source to Drain. 1 path of conduction. Field Effect; Refers to the Depletion Field formed around the PN junction. JFET & MOSFET

3. JFET; Junction Field Effect Transistor. 1. Operates in the Depletion only mode. 2. Conducts W/0v on the Gate. 3. Reversed Biased for Operation. MOSFET; Metal Oxide Semiconductor Field Effect Transistor. 1. Can operate in the Depletion or Enhancement Mode. 2. Conducts W/0V on the Gate. 3. Reversed or Forward Biased for Operation. 4. Also Known as an, IGFET. MOSFET, [Enhancement only Mode]; 1. Operates in the enhanced only mode. 2. Conducts w/a Positive on the Gate. A channel must be formed to allow for conduction. 3. Forward Biased for Operation. 4. Also Known as an, IGFET. Field Effect Transistors JFET & MOSFET ; Bi & Uni-Polar

4. Field Effect Transistors Bipolar & Unipolar Comparison; GATE DRAIN SOURCE UNIPOLAR TRANSISTOR N P S G D COLLECTOR BASE EMITTER BIPOLAR TRANSISTOR N N P C E B JFET Operation

5. P P N N -6 v P P N N -2 v P P N N 0 v I Field Effect Transistors JFET JFET; Reverse Bias  or Voltage @ the Gate . Resistance , Current , E @ the Drain . GRIDGRID 0000 0000 Schematic Symbol

6. Field Effect Transistors JFET JFET; Schematic Symbols. Source GATE Drain N-Channel JFET Source GATE Drain ASYMETRICAL Wiring Integrity must be observed Source GATE Drain P-Channel JFET DRAIN GATE SOURCE SYMETRICAL Source & Drain Wiring can be reversed IGFET Construction

7. N DRAIN SOURCE SUBSTRATEINSULATORMATERIAL DRAIN SOURCE N N P DRAIN N P N SOURCE METAL GATE Field Effect Transistors MOSFETIGFET MOSFET, [IGFET]; Construction. Depletion Mode

8. DRAIN SOURCE N P N ++++++++++++++++++++++++++ N-material Channel Negative on the Gate depletes the channel of current carriers -------------- METAL GATE INSULATING MATERIAL Field Effect Transistors DEPLETION MODE MOSFET DEPLETION MODE MOSFET; Operation like the JFET. GRIDGRID 0000 0000 Enhanced Mode

9. N P N DRAIN SOURCE ++++++++++++++ -------------------- N-material Channel Positive on the Gate adds current carriers to the channel METAL GATE INSULATING MATERIAL Field Effect Transistors ENHANCEMENT MODE ENHANCEMENT MODE MOSFET; GRIDGRID +0 ++00++000 Enhanced only Mode

10. MOFET SCH Symbols TII Field Effect Transistors Field Effect Transistors ENHANCEMENT ONLY ENHANCEMENT ONLY MODE MOSFET GRIDGRID +0 ++00++000 Creates negative ion Field ++++++++++++++ -------------------- -------------------- -------------------- ++++++++++++++ ++++++++++++++ Creates Electron Channel DRAIN SOURCE N P N W/ 0V @ the Gate the device is OFF, [ no Current flow].

11. Field Effect Transistors Schematic Symbols MOSFET Schematic Symbols; MOSFET Depletion & Enhancement N-channel MOSFET Enhancement only. N-channel MOSFET Enhancement only. P-channel JFET Ckt Comp

12. V DD R D R S R G V S I D Field Effect Transistors JFET Circuit; Support components; JFET AMP

13. Troubleshooting procedure Field Effect Transistors JFET Amplifier; Support Component Identification. R12 R1 & 2; AC Voltage Divider R3 R3; Gate-Source Bias, Ensures a very short TC so C1 does not fully charge & 0V on the Gate. R4 R4; Drain load, Develops the Ckt Gain. R5 R5; Source - Gate Bias. C3 C3; Prevents signal degeneration. C12 C1 & 2; Input & Output Coupling Caps. R6 R6; Adjust output Amplitude. + R3 2.2 M  R2 7.5 K  R1 100 K  R5 1 K  E O T C2 C3 Q1 2N5484 R4 3.9 K  2 3 4 5 6 7 R6 50 K  C1.05  f

14. Challenge Field Effect Transistors JFET Amplifier; Troubleshooting procedure. + R3 2.2 M  R2 7.5 K  R1 100 K  R5 1 K  E O T R4 R6 C1 C2 C3 Q1 2N5484 3.9 K  2 3 4 5 6 7 50 K .05  f 9.28 VDC 0 VDC.672 VDC 2nd 1st 3rd 5th 4th

15. Challenge Field Effect Transistors JFET Amplifier; Troubleshooting Challenge #1. + R3 2.2 M  R2 7.5 K  R1 100 K  R5 1 K  E O T R4 R6 C1 C2 C3 Q1 2N5484 3.9 K  2 3 4 5 6 7 50 K .05  f 9.28 VDC 0 VDC.672 VDC 0 VDC

16. Challenge Field Effect Transistors JFET Amplifier; Troubleshooting Challenge #2. + R3 2.2 M  R2 7.5 K  R1 100 K  R5 1 K  E O T R4 R6 C1 C2 C3 Q1 2N5484 3.9 K  2 3 4 5 6 7 50 K .05  f 9.28 VDC 0 VDC.672 VDC 2.54 V 0 VDC 2.54 V

17. Review ? Field Effect Transistors JFET Amplifier; Troubleshooting Challenge #3. + R3 2.2 M  R2 7.5 K  R1 100 K  R5 1 K  E O T R4 R6 C1 C2 C3 Q1 2N5484 3.9 K  2 3 4 5 6 7 50 K .05  f 9.28 VDC 0 VDC.672 VDC 2.48 V

18. Field Effect Transistors Review Questions; ___________________________ 1.The most significant advantage of the field effect transistor is that no ___________ flows from ________ to ________. ________________ 2.The above advantage allows the FET to display the important characteristic of _______ input _________. ________ 3.All JFETs operate in the ________ mode. _________________ 4.What will happen to the current in an N Channel MOSFET when a positive voltage is applied to the Gate ? _________________ ____ 5.On PC 49 card, what is the phase relationship of Q1 Gate to Drain? ____ 6.What condition must be present for a JEFET to operate normally?_________________________________ ______________ 7.What direction does current flow in an FET? ______________ Answers

19. Field Effect Transistors Review Questions; ___________________ 8.Which type of FET must have a voltage applied to the Gate to create a channel ? ___________________ ________ operated transistor. 9.The FET is a ________ operated transistor. _____ 10.What value would be measured @ the source if R5 were to open? _____ ____polar 11.A transistor for which only one Majority current carrier need be considered during normal operation is said to be ____polar. _________ _________ ________ 12.What are the FET terminals called? _________ _________ ________ Answers