Transistor MOS

1) Describe the structure of a NMOS to enrichment:

A condenser MOS is had constituted from a metal, an oxide and a p_doped, ai heads della oxide we have two drugged regions n connected ai clips of Drain and of Source, applying a positive tension al gate is had that in a first time the below region is emptied of gaps after which al to grow of V_G is arrived to having a channel of minority bearers that concurs the electron flow dal Source al Drain.

 

2) approximate Analysis of_{the DS} with the control of loads:

The current_{the D} that slides in the channel is given simply from the relationship between loads Q_n and the T time_tr that it employs to cross the channel, in particular has while replacing ha

 

3) complete Analysis of_{the DS} with the control of loads:

In this case the fall is not neglected of upgrades them that it is had along the channel, however in order to simplify the trattazione uses the approximation of gradual-channel second which the fields in the direction y (…from the Drain to the Source) are infinitesimal regarding that they are had in direction x (…from the gate ones to the bulk) moreover is assumed that the length of the L channel is greater of the length of the region of emptying to the Drain. The fall of upgrades them to the inside of a feature of the having channel R resistance is where replacing is obtained , integrating for separation of the variable ones and replacing the value of m_n is obtained draft of parabolas that express_{the D} to varying of V_G however they only have value for V_DS < V_G â " V_T beyond in fact implies an improbable conductance differentiates them negative and it loads not negative in the channel. However for V_DS > V_G â " V_T is had that the channel is interrupted close to the drain and therefore a fort is created electric field who ago that the speed of the bearers is maximum and constant therefore_{the DS} are constant and insensitive to V_{the DS} its value in this region of operation is in fact .

 

4) Determination of V_T :

The NMOS in saturation is put cortocircuitando the Gate with the Drain, therefore from the draft of a straight one can be designed to the characteristic of to varying of V _D that intersects the abscissa in V_T and whose slope can be used in order to determine mobility.

 

5) Body Effect:

As for the determination of V_T also in this case the NMOS in saturation is placed cortocircuitando the Gate with the Drain moreover applies one tension V_B to the bulk, to its to grow is had that the straight one that represents to varying of V_D trasla in parallel with if same and therefore to growing of V_B it increases also V_T .

5) Transconduttanza:

It can be calculated deriving the I_D regarding V_G obtains per V_D < V_{S sat} .

 

6) Time of transit:

The time of transit in the channel of a MOS in having saturation the Source to mass is estimated with the integral where and V_C pu² to be gained resolving for separation of variable the equation differentiate them , is obtained that replaced and integrated it supplies .

 

7) CMOS:

It is a circuit constituted from a PMOS and a having NMOS the Drain in common while the Source of the PMOS is to V_SS while the Source of the NMOS is to mass, the Gate instead is cortocircuita to you and to they it comes applied marks them of income while the escape is taken on the Drain. The main characteristic of this configuration is that one of the two MOS only absorbs current during the commutations in how much alternatively is interdetto and the other is in active region.