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News; MOS introduction

Published: Thursday 19 May, 2016

MOS working principle --MOS pipe introduction
MOS tube, that is, in the integrated circuit insulation of the field effect tube. MOS English name -- the metal - oxide - semiconductor, the exact said, the name describes the integrated circuit MOS structure, namely: in the structure of the semiconductor device, plus silica and metal, forming a gate electrode. MOS pipe source and drain can be reversed, is formed in the P type N type area in backgate. In most cases, the two areas is the same, even if both ends swap also does not affect the device performance, such devices is assumed to be symmetric.
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MOS tube profile
2 MOS pipe working principle of the structure of the --Mos pipe
MOS tube internal structure as shown below; the conduction only a polarity of the carrier (sub) in electrical conductivity, is unipolar transistor. Conductive mechanism and small power MOS tubes of the same, but structure has larger difference, small power MOS tube is horizontal conductive devices, power MOSFET mostly adopts the vertical conductive structures, also known as VMOSFET, greatly improving the breakdown voltage of the MOSFET and high current capability.
Structural characteristics of Mos tube
The main characteristic is that there is a layer of silicon dioxide insulating layer between the metal gate and the channel, so it has a very high input resistance, which forms the N type conductive channel in the two high concentration n diffusion region. N channel enhanced MOS tube must be applied forward bias on the grid, and only when the gate source voltage is greater than the threshold voltage, the N channel MOS. The N channel depletion type MOS pipe is a n channel MOS tube which is produced by a conductive channel when the voltage of the gate source voltage is zero.
3 MOS tube working principle of the characteristics of --MOS pipe
Input and output characteristics of 3.1MOS tube
For the circuit of the common source electrode, the source electrode and the substrate are isolated by the silicon dioxide isolation layer, so the grid current is 0.
Characteristics of MOS tube
Figure (a) is a common source connection circuit, output characteristic curve is shown.
When VGS
Characteristics of MOS tube
Conduction characteristics of 3.2MOS tube
MOS tube as a switching element, the same is working in the cut-off or conduction through two states. Because the MOS tube is a voltage control element, the main source voltage uGS is determined by the gate voltage. Below to NMOS tube as an example to introduce its characteristics.
Characteristics of MOS tube
Figure (a) is a switching circuit composed of NMOS enhanced tube.
NMOS characteristic, Vgs is greater than a certain value will guide, suitable for use in the source ground when the situation (low end driver), as long as the gate voltage to achieve 4V or 10V on it.
PMOS characteristics, Vgs is less than a certain value will guide, suitable for use in the case of source VCC (high end driver). However, although PMOS can be very convenient to use as a high-end driver, but due to the large resistance, high prices, less replacement and other reasons, in the high-end driver, usually still use NMOS.
4 MOS tube working principle
The working principle of MOS transistor (N channel enhancement mode MOS field effect transistor) it is the VGS to control how much "induced charges", to change the formation by these "induced charges" conductive channel, then controlled drain current. In the manufacture of the tube, through the process of the insulation layer in the emergence of a large number of positive ions, so on the other side of the interface can induct more negative charge. The negative charge to hypertonic impurity region n is switched on, the formation of the conductive channel, even in the VGS=0 also larger drain current ID. When changing the gate voltage, the channel is also changes the amount of charge induction, the width of the conductive channel change and leakage current ID changes with the change of gate voltage.
Working principle of MOS tube
Knowledge extension
Classification of MOS tubes
According to the channel material type and insulation gate type the n-channel and p-channel two; according to the electric mode: MOS tube is divided into depleted and enhanced, so MOS field effect transistor n-channel depletion type and enhanced; P - channel depletion type and enhanced four major categories. Classification of MOS tubes by classification of MOS tubes
MOS tube application
The most prominent characteristic of MOS tube is good switching characteristic, so it is widely used in the circuit of electronic switch, such as switching power supply and motor drive, and the lighting dimming. And by MOS tube CMOS sensors provide increasingly high quality camera, the achievements of the more "photographer".
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