Transistor Devices Quiz

Study Notes

A BJT is a three terminal device with terminals labeled Source, Drain, and Gate.

JFET's are a type of field-effect transistor that utilize a junction between a semiconductor and a metal to control current flow.
Common Source (CS) configuration:
- Most common mode of operation.
- High input impedance.
- High voltage gain.
- Used in audio frequency amplifiers.
- Output signal is 180 degrees out-of-phase with the input.
Common Gate (CG) configuration:
- Input terminal is the Source.
- Output terminal is the Drain.
- Low input impedance.
- High output impedance.
- Used in high frequency and impedance matching circuits.
- Output signal is 0 degrees in-phase with the input.
Common Drain (CD) configuration:
- Input terminal is Gate.
- Output terminal is Source.
- High input impedance.
- Low output impedance.
- Near-unity voltage gain.
- Used in buffer amplifiers, also called source followers.
- Output signal is 0 degrees in-phase with the input.

MOSFETs are voltage-controlled devices with higher input resistance than JFETs.
JFETs have a continuous channel, while MOSFETs have a channel that only exists in the depletion mode.
JFETs are less susceptible to damage than MOSFETs because of the presence of metal oxide.
MOSFETs have a higher signal handling capacity than JFETs.
MOSFETs are more expensive to manufacture due to the use of metal oxide.
The gate terminal of a MOSFET is insulated from the channel, while the gate terminal of a JFET is directly connected to the channel.
JFETs have a more flat characteristics curve than MOSFETs.
The conductivity of a JFET is controlled by the reverse bias of the gate, while the conductivity of a MOSFET is controlled by the charge carriers induced in the channel.