AnonymousPT said:What about JFET? There is no such insulating layer between the gate and the channel.. Then?
A field effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current. It has three terminals: source, drain, and gate, and is commonly used in electronic devices for amplification and switching.
The main difference between a FET and a BJT is the way they are controlled. In a FET, the electric field controls the flow of current, while in a BJT, the current is controlled by the amount of current flowing into the base terminal. Additionally, FETs have a higher input impedance compared to BJTs, meaning they require less input current to control the output current.
A high input impedance in a FET means that it requires a very small amount of input current to control the output current. This makes FETs ideal for use in high-frequency applications as they do not load down the input signal.
There are three main types of FETs: junction field-effect transistors (JFETs), metal-oxide-semiconductor field-effect transistors (MOSFETs), and insulated-gate field-effect transistors (IGFETs). Each type has its own unique structure and characteristics, but they all operate on the principle of using an electric field to control the flow of current.
The main advantages of FETs include high input impedance, low noise, and high gain. They also have a simpler structure compared to BJTs, making them easier to manufacture. However, FETs have a lower current handling capacity and are more susceptible to damage from static electricity. They also tend to be more expensive compared to BJTs.