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
Professional engineers engage with a wide range of technically advanced and complex problem. So technical know-how is necessary to solve problems, advance existing technologies and

Convert number systems from one base to another, and apply the binary number system to logic circuits 1.   Convert the following decimal numbers to binary a.   81 10 b.

Explain immediate data addressing mode (with examples) available in microprocessors. Immediate Mode: The operand given in immediate mode is the actual data itself.

Illustrate the construction and working of:- (i) Pressure Thermometer (ii) Selective Radiation Pyrometer (iii) Thermistor (iv) Laws of Thermocouple

Q. You are to construct a modified truth table for the circuit realization of the SRFF shown in Figure. As indicated in the text, you guess an output and then go back ato check it

material to produce analog oscilloscope

Q. What is Output Impedance? Output Impedance : The output impedance of an amplifier is a measure of the impedance or resistance. It has nothing to do with the actual loading t

Signals in Noise: Let us now consider a weak information signal that is to be amplified by a noisy amplifier. The signal-to-noise ratio (SNR), usually expressed in decibels, be

What are the basic operations of a computer? The basic operations are READ and WRITE.

ON output plot of a JFET n-channel transistor if ID is close to IDSS does the value of VGS close to VP?