number of the output transistors

[drabos]

What are the main reasons in the decision about the numbers of the transistors in an output stage?

So, using 10 MOSs or 20 MOSs or more...

Thanks,

 

[A.Anand Srinivasan]

it is mainly the consideration on the output capacitance and the power sourcing capability...

 

[pichuang]

A.. Anand Srinivasan is right. The more output transistors (we call it fan out devices), the more capacitance. I am not too sure about Analog IC, but in digital IC it is often a better practice to limit the number of fan out devices to be less than 4 whenever possible.

 

[sohiltri]

For MOS transistor fanout of 50 is possible....It all depends on total load capacitance offered.....more the fanout slower the device....
But How power sourcing capability will affect Fanout in MOS?

 

[A.Anand Srinivasan]

more MOS means the power supply should be capable of supplying a lot of power especially when the MOS undergoes transition....

 

[ameed]

hi all,

The more output transistors (we call it fan out devices), that will effect on directly the more capacitance.

about Analog IC, but in digital IC it is often a better practice to limit the number of fan out devices

to be less than 4 whenever possible.

thanx....