Fet operation, Electrical Engineering

FET operation:

1585_FET operation.png

Figure: I-V characteristics and output plot of a JFET n-channel transistor.

The FET manages the flow of electrons (or electron holes) from the source to drain by influencing the size and shape of a "conductive channel" created and affected by voltage (or lack of voltage) applied across the gate and source terminals (For easiness of discussion, this assumes body and source are related). This conductive channel is the "stream" by which electrons flow to drain from source.

A negative gate-to-source voltage causes a depletion region to expand in width and encroach on the channel from the sides, narrowing the channel, in an n-channel depletion-mode device. If the depletion region expands to fully close to channel, the resistance of the channel from source to drain turns large, and the FET is efficiently turned off like a switch. Similarly a positive gate-to-source voltage raises the channel size and permits electrons to flow easily.

On the other hand, in an n-channel enhancement-mode device, a positive gate-to-source voltage is essential to create a conductive channel, because one does not exist naturally within the transistor. The positive voltage that is attracts free-floating electrons within the body towards the gate, creating a conductive channel. But first, sufficient electrons must be attracted near the gate to counter the dopant ions added to the body of the FET; this makes a region free of mobile carriers called a depletion region, and the phenomenon is considered to as the threshold voltage of the FET. Further gate-to-source voltage rises will attract even much more electrons towards the gate that are able to create a conductive channel from source to drain; this process is termed as inversion.

Posted Date: 1/11/2013 4:48:47 AM | Location : United States







Related Discussions:- Fet operation, Assignment Help, Ask Question on Fet operation, Get Answer, Expert's Help, Fet operation Discussions

Write discussion on Fet operation
Your posts are moderated
Related Questions
List the uses of USART. USART- Universal Synchronous Asynchronous Receiver-Transmitters. It is used to transmit and receive the data in serial communication mode. It is

Technical Losses in Power Systems The technical losses in power systems occur because of energy dissipated in the conductors and equipment used for transmission, transformat

T h er e are three main types -   The Shunt Connected DC motor in which the armature coils are connected in parallel with the field coils   The Serie

draw a graph of V=IR for R=300ohms over the domain -3mA

Core Functionalities of the GIS: The GIS should be able to: 1          Create layers from all supported data sources involving coverage feature classes, shape files, compu

Q. Explain Repetitive coverage of satellite? Due to repeated passes of the satellite over the same reach, data is repeatedly acquired. Therefore, comparisons of a dynamic pheno

Q. Determine the Thevenin resistance viewed from terminals A-B of the circuit of Figure by setting independent sources to be zero and applying a test voltage at terminals A-B.

Explain explanatory notes on comparison of RS232C and RS422A standards. Comparison of RS232C and RS422A standards: RS232C 1. Standard explained for asynchronous commu

Particles of mass M and m separated in space by a distance R exert a mutually attractive gravitational force F on one another given by where G is the universal gravitationa

Factors which affect the inductance of an inductor include:  i)  The number of turns of wire (N) - more turns the higher the inductance ii)  The cross-sectional area of the