1. BJT transistors

2. Darlington Transistors
Allow for much greater gain in a circuit
β = β1 * β2

3. FET Transistors Analogous to BJT Transistors
FET Transistors switch by voltage rather than by current
BJT
FET
Collector
Drain
Base
Gate
Emitter
Source
N/A
Body S G D

4. FET Transistors FET (Field Effect Transistors)
MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor)
JFET (Junction Field-Effect Transistor)
MESFET
HEMT
MODFET
Most common are the n-type MOSFET or JFET

5. FET Transistors – Circuit Symbols
MOSFET
In practice the body and source leads are almost always connected
Most packages have these leads already connected B S G D B S G D
JFET S G D

6. FET Transistors – How it works
The “Field Effect”
The resulting field at the plate causes electrons to gather
As an electron bridge forms current is allowed to flow
Plate
Semi-conductor

7. FET Transistors JFET MOSFET source drain gate source drain gate P N N

8. FET Transistors – Characteristics
Current flow B S G D

9. Transistor Uses
Switching
Amplification
Variable Resistor

10. Input characteristicsIB IB
VBE
0.7V
Acts as a diode
VBE 0.7V

11. Output characteristics
IB = 40mA
IB = 30mA
IB = 20mA
IB = 10mA
VCE
Early voltage
Cutoff
region
At a fixed IB, IC is not dependent on VCE
Slope of output characteristics in linear region is near 0 (scale exaggerated)

12. Biasing a transistor
We must operate the transistor in the linear region.
A transistor’s operating point (Q-point) is defined by
IC, VCE, and IB.

13. Thank You