What are field effect transistors?
Unlike bipolar transistors, field effect transistors use only one type of load carriers (electrons or gaps) flowing through a semiconductor channel. If in bipolar transistors the conductivity control is achieved by varying a current between the emitter and the base, in field effect transistors the conductivity control is achieved by varying a voltage applied to a control electrode called gate or gate (with a role similar to the TB base).
Operation of field effect transistors
The operation of field effect transistors is based on changing the conductivity of a channel made of a semiconductor material by applying an electric field created by the voltage applied to the control electrode (grid or gate). The control of the electric current by an electric field is called the field effect.
Field effect transistors have the following advantages over bipolar transistors:
- has a very high input impedance (because they are voltage controlled)
- can be used as voltage controlled resistors
- good linearity of the circuit
- reduced noise
- reduced size
Depending on how the channel is made (in volume or on the surface), field effect transistors are divided into two categories:
- field effect transistors with junction grid (TEC-J)
- Isolated Grid Field Effect Transistors (TEC-MOS)
Depending on the type of channel doping, TEC-J transistors fall into two categories:
- TEC with junction grid with channel n
- TEC with junction grid with channel p
Depending on the realization of the channel, the TEC-MOS transistors are divided into two categories:
- TEC with insulated grid with initial channel
- TEC with insulated grid with induced channel
For a better understanding of use and functionality of MOSFET transistors, I have attached the video below: