Explains how Field Effect Transistors work

2. P N P

3. P N P
extra electronsmissing
electrons

4. P N P

5. P N P

6. P N P
No extra or missing electrons
prevents charges from flowingIons

7. Depletion Zones

9. source
drain
gate
gate

10. source
drain
gate
gate
electron flow
conventional flow

11. What happens if … ?

12. source
drain
gate
gate

13. source
drain
gate
gate

14. source
drain
gategate

15. source
drain
gategate
signal
input

16. source
drain
gategate
signal
input

17. source
drain
gategate
signal
input

18. source
drain
gategate
signal
input
signal
output

19. FET properties
• Field effect transistors control current flow by
varying voltage level
– Voltage controlled device
• Practically no current to operate
– Ideal amplifier draws no current from a source
• High input impedance
– no gate/source current because reverse biased
• Low output impedance
– Easy current flow through center channel

21. N channel JFET P channel JFET

23. source
drain
gategate
MOSFET
Metal Oxide Semiconductor Field Effect Transistor
thin silicon
metal oxide
layer
between
N and P
material

24. source
drain
gategate
depletion mode MOSFET

25. source
drain
gategate
enhancement mode MOSFET

26. MOSFET properties
• Nearly infinite impedance
– Does not load a source
– Very low current draw
• Low noise
• Ruined by static discharge
– Shipped in protective foil and conductive foam
– Handle by case not pins
– Everything grounded when working with them
– Power off when inserting or removing

27. depletion mode enhancement mode
N Channel MOSFET N channel MOSFET
depletion mode enhancement mode
P Channel MOSFET P channel MOSFET