A noise analysis example in Razavi's book.

[D2004]

The following attached file is a noise analysis example in Razavi's book "Design of analog cmos ICs" at page218-219.

I think, in Eq(7.38 ) , the last term RD^2 should be (RD||r0)^2, where r0 is the output resistance of M1.

Is it right?

 

[vale]

r0>>RD, so being omitted

 

[ezt]

Hi.
I think ro assumed infinite. Dr. Razavi has made this assumption many times in his book. But in general, yes you are right.

Regards,
EZT

 

[layes2]

yes r0>>rD

 

[sgperzoid]

Although it is not so correct that the output resistance could be assumed to be infinite. However, for general analysis purpose, you can just ignore it coz its function is just the same as the load resistor

 

[D2004]

That sounds reasonable, although I don't find any this assumption Dr. Razavi made in the book.

Anyone has the idea on the values or ranges of r0 and RD in practice?

 

[sgperzoid]

That sounds reasonable, although I don't find any this assumption Dr. Razavi made in the book.

Anyone has the idea on the values or ranges of r0 and RD in practice?

OK, it depends on the process u r using.
In RF applications where short channel MOSFET are needed, the output resistance of the MOSFET is quite low compared to analog MOSFET

typically, for 0.18 process, it is not surprising that the output resistance drop to several hundred Ohm. You may find this value in some papers also.