Field-effect transistors (FET) behave as voltage-controlled resistors and can be group into three major categories. Which option is NOT one of these categories?
depletion-mode MOSFETs
Biased field-effect transistors (BFETs)
enhancement-mode MOSFETs
junction field-effect transistors (JFETs)
Answers
A cluster of field effect transistor
A cluster of field effect transistor
Field effect transistor or FET is a transistor, where output current is controlled by electric field. FET sometimes, is called uni-polar transistor as it involves single carrier type operation. The basic types of FET transistor is completely different from BJT transistor basics. FET is three terminal semiconductor devices, with source, drain and gate terminals.
The charge carries are electrons or holes, which flow from the source to drain though an active channel. This flow of electrons from source to drain is controlled by voltage applied across the gate and source terminals.
Types of FET Transistor
FETs are of two types- JFETs or MOSFETs.
Junction FET
A Junction FET
A Junction FET
The Junction FET transistor is a type of field effect transistor that can be used as an electrically controlled switch. The electric energy flows through an active channel between sources to drain terminals. By applying a reverse bias voltage to gate terminal, the channel is strained so the electric current is switched off completely.
The junction FET transistor is available in two polarities which are;
N- Channel JFET
N channel JFET
N channel JFET
N channel JFET consists of an n type bar at the sides of which two p type layers are doped. The channel of electrons constitutes the N channel for the device. Two ohmic contacts are made at both ends of the N-channel device, which are connected together to form the gate terminal.
The source and drain terminals are taken from the other two sides of the bar. The potential difference between source and drain terminals is termed as Vdd and potential difference between source and gate terminal is termed as Vgs. The charge flow is due to flow of electrons from source to drain.
Whenever a positive voltage is applied across drain and source terminals, electrons flows from the source ‘S’ to drain ‘D’ terminal , where as conventional drain current Id flows through the drain to source. As current flows through the device, it is in on state.
When a negative polarity voltage is applied to the gate terminal, a depletion region is created in the channel. The channel width is reduced, hence increasing the channel resistance between the source and drain. Since the gate source junction is reverse biased and no current flows in the device, it is in off condition.
So basically if voltage applied at the gate terminal is increased, less amount of current will flow from the source to drain.
The N channel JFET has greater conductivity than the P channel JFET. So the N channel JFET is more efficient conductor compared to P channel JFET.