FET ( Field Effect Transistor) 1. Unipolar device i. e. operation depends on only one type of charge carriers (holes or electrons) 2. Voltage controlled Device (gate voltage controls drain current) 3. Very high input impedance (10 9 -10 12 ) 4. Source and drain are interchangeable in most Low- frequency applications 5. Low Voltage Low Current Operation is possible (Low-power consumption) 6. Less Noisy as Compared to BJT 7. No minority carrier storage (Turn off is faster) 8. Self limiting device 9. Very small in size, occupies very small space in ICs 10.Low voltage low current operation is possible in MOSFETS 11.Zero temperature drift of out put is possible. Few important advantages of FET over conventional Transistors
FET ( Field Effect Transistor). Few important advantages of FET over conventional Transistors. Unipolar device i. e. operation depends on only one type of charge carriers ( holes or electrons) Voltage controlled Device (gate voltage controls drain current) - PowerPoint PPT Presentation
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FET ( Field Effect Transistor)
1. Unipolar device i. e. operation depends on only one type of charge carriers (holes or electrons)
2. Voltage controlled Device (gate voltage controls drain current)3. Very high input impedance (109-1012 )4. Source and drain are interchangeable in most Low-frequency applications5. Low Voltage Low Current Operation is possible (Low-power consumption)6. Less Noisy as Compared to BJT7. No minority carrier storage (Turn off is faster) 8. Self limiting device9. Very small in size, occupies very small space in ICs10. Low voltage low current operation is possible in MOSFETS 11. Zero temperature drift of out put is possible.
Few important advantages of FET over conventional Transistors
JFET
MOSFET (IGFET)
n-Channel JFET
p-Channel JFET
Types of Field Effect Transistors (Classifications)
n-Channel EMOSFET
p-Channel EMOSFET
Enhancement MOSFET
Depletion MOSFET
n-Channel DMOSFET
p-Channel DMOSFET
FET
Figure: n-Channel JFET.
The Junction Field Effect Transistor (JFET)
Gate
Drain
Source
JFET SYMBOLS
n-channel JFET
Gate
Drain
Source
n-channel JFET(Offset-gate symbol)
Gate
Drain
Source
p-channel JFET
Figure: n-Channel JFET and Biasing Circuit.
Biasing the JFET
Figure: The nonconductive depletion region becomes broader with increased reverse bias.
(Note: The two gate regions of each FET are connected to each other.)
Operation of JFET at Various Gate Bias Potentials
P P +
-
DC Voltage Source
+
-+
-
N
N
Operation of a JFET
Gate
Drain
Source
Figure: n-Channel FET for vGS = 0.
Simple Operation and Break down of n-Channel JFET
Figure: If vDG exceeds the breakdown voltage VB, drain current increases rapidly.
Break Down Region
N-Channel JFET Characteristics and Breakdown
Figure: Transfer (or Mutual) Characteristics of n-Channel JFET
2
1
P
GSDSSDS V
VII
IDSS
VGS (off)=VP
Transfer (Mutual) Characteristics of n-Channel JFET