what function do the five serial transistors act as ?

[samuel]

Note: (1)serial transistors have same length .
(2)their gates are connected together.
(3)the last Nmos transistor drain is connected to gate

thanks.


samuel.

 

[renwl]

diode

 

[bunalmis]

May be for zener function.

 

[cougar168]

I guess it is part of a cuurent mirror

 

[Humungus]

in some case association of transistors in series improve matching when designing a current mirror with big mirroring factor.

For instance imagine you must create a current 9 time the input one. Then you connect 3 MOs as you described with the gate connected to the gate of 3 MOS connected in parallel. In that case you can see that the ideal mirroring factor is 9.

As the chrerry on the cake, you get that the area of both elements of the mirror have the same effective surface, then optimizing matching.

 

[eda4you]

it is a simple diode. maybe the lenght of the overall transistor is to large for the drc. I had some problems once time and ahd also to split it into shorter ones and connected in series. the interesting was that it was noit realy a design rule violation, it was only give because the transistor simulation model was not modeld for so long mosts and so the implemented such a rule, to split it.

 

[samuel]

thanks, eda4you

i feel that its answer is ok.