Monday, May 20, 2019

Field-Effect Transistor Overview

Introduction
    
     Field-Effect Transistor is a three terminal device that has used in the semiconductor industry. It controls a voltage(unlike Bipolar Junction Transistor, current control). FET 3 terminals are a drain, source, and gate. The voltage on drain creates an electric field that creates an electric field to control a current flowing through a channel in a semiconductor.  In a large scale of development technology, it has a product that is useful I many semiconductor applications like gadgets and smartphone. Also, its operation has good on (Radio Frequency) RF technology and power control, also for a switch for general amplification.


Brief Explanation and Types

     Three terminals of FETs are known as Source, Drain and Gate.


     Field-Effect Transistor classifies into three,  a junction field-effect transistor(JFET), a metal-oxide-semiconductor field-effect transistor (MOSFET), and a metal-semiconductor field-effect transistor(MESFET).

     Due to the inherent sensitivity of the impedance of the drain source to the source voltage of the gate, the JFET can actually be used as a voltage control resistor.

   There are two types of MOSFET: depletion and enhancement. Each of MOSFET has transfer characteristics and this FET are similar to the transfer characteristic of JFET. The drain of MOSFET is continue but JFET can end.  The transfer characteristics is up to the IDSS level.

   The aarrow part of a JFET or MOSFET symbol of channel n always points to the center of the symbol, while that of channel p devices always lies outside the symbol.

 

   The vertical metal oxide and silicon FET (VMOS), a layer of SiO2 that locate in between the gate and the p-type region,is a metal surface connection to the terminal of the device, drain and source for the inductive n-type inductive channel growth . (Operation in improvement mode) VMOS has a positive temperature coefficient and there is the possibility of thermal leakage. The switching is faster than the traditional configuration.

   CMOS (complementary MOSFET) uses a unique combination of a pair of external leads, a p-channel MOSFET and a n-channel MOSFET. One of characteristics of CMOS is very high input impedance, other is fast switching speeds and low power levels of operation, CMOS is very useful in digital or logic circuits.

   The depletion type MESFET includes a metal-semiconductor junction, and as a result, characteristics can be obtained that match the characteristics of the n-channel depletion-type JFET. There are also MOSFET type enhancement features.

   MOSFETs are the most common transistors in digital circuits, and memory chips or microprocessors may include hundreds or hundreds of millions. Because it can be made of p-type or type semiconductors, complementary Mos transistor pairs can be used to implement switching circuits with very low energy consumption of CMOS logic.

     Microprocessor architecture A microprocessor is a unique IC packet in which many useful functions are incorporated and converted into a single silicon semiconductor chip. Its architecture consists of a central processing unit, memory modules, a bus system and input / output devices.

Conclusion

     Important characteristics of Field-Effect Transistor (FET) is its high input impedance (mega Ohms) compared to that of BJT (Kilo Ohms).


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