Field Effect Transistors Flashcards
What is the full form of FET ?
Field Effect Transistors
How many terminals does a FET have ?
3
How do FETs control the shape and electrical conductivity of a channel ?
By using an electric field
What are the two types of FETs ?
JFET and MOSFET
What is the full form of JFET ?
Junction FET
What is the full form of MOS FET ?
Metal Oxide Semiconductor FET
What are the two types of MOS FETs ?
Depletion MOS FETs
Enhancement MOSFETs
What controls a BJT ?
Current
Why is a BJT a current controlled device ?
Output (Collector Current) depends on input current(Base current)
What controls a FET ?
Voltage
Why is a FET a voltage controlled device ?
The output (drain current) depends on gate-source voltage
What are the three terminals of a BJT called ?
Base, Emitter and Collector
What are the three terminals of a FET called ?
Gate, Source and Drain
Which charge carrier causes current in a BJT ?
Both holes and electrons
Which charge carrier causes current in a FET ?
Either holes or electrons
Why are FETs called unipolar charge transistors ?
Either of the charge carriers causes current, but not both
Why are FETs used in noise sensitive electronics in tuners and low noise amplifiers in satellite receivers ?
It produces less noise than a BJT
What is another reason FETs are used in satellite receivers ?
It is relatively immune to radiation
What makes FETs excellent signal choppers ?
No offset voltage at zero drain current
Which transistor has better thermal stability, BJT or FET ?
Generally, FET
What is the main advantage of a FET over a BJT ?
It’s high input impedance
How high is a FET’s input impedance, generally ?
It is of the order of 100 M ohm
Why do MOSFET’s need special handling during installation ?
They are susceptible to overload voltages
Why is a MOSFET vulnerable to electrostatic damage during installation ?
It’s fragile insulating layer in between the gate and the channel
Which transistor has a high gain-bandwidth product ?
BJT has higher gain-Bandwidth product
Which transistor has better thermal stability ?
FETs have better thermal stability
What are the two main configurations of JFETs ?
N channel and P channel JFET
Describe the drain and source
Two ohmic electrical resistances at either end
Describe the channel
A narrow piece of high resistivity semiconductor
What is the purpose of the channel ?
A path for the majority carriers to flow form the source to drain
What is the gate terminal in a N- channel JFET ?
The two embedded P type layers are connected together
How is the drain current controlled for a given potential in between the drain and source ?
By externally applied potential in between source and drain V (dd)
