Question about resistance in the source, drain, ...

Hi. I have some trouble in understanding resistance.
The reference is 'CMOS Circuit Design, Layout, and Simulation' by Baker. (1E)

In the chapter 22 Amplifiers
Vout/Vin = (resistance in the drain) / (resistance in the source).

Now, I want to find the resistance in the drain and resistance in the source of
common source amplifier.
(The amp is composed of M1(NMOS) and M2(PMOS).
M1 gate : Vin, M1 source : VSS, M1 drain : Vout
M2 gate : Vout, M2 source : VDD, M2 drain : Vout)

The answer is,
the resistance looking into the source of M1 is 1/gm1 and
the resistance looking into the drain of M1 is 1/gm2.

I cannot understand how to find these. Please help me.

I dont have the same book, so I dont know the exact amplifier you are referring to, but if you go and set up the small signal model of the FETs in the circuit, and then do the analysis like that, finding the input current and voltage, as well as the output current and voltage will be all the information you need, as you can just use the relationship V/I = R to find both your input and output resistance.

The book I have is Sedra/Smith and is called "Microelectronic Circuits"
Single-Stage Discrete MOS amplifiers are covered in chapter 4 secion 4.7 and there is a pretty full description of how to analyze these circuits. If you dont know what the small signal model is, you should probably look that up if you are going to need to know how to analyze these circuits more, but if not, I can try to quickly explain it to you...

oh, thank you for your reply.
But I know how to analyze small-signal model.

That I want to know is how to find the resistances intuitively.

For example, here is a common-source amp.

.......VDD
.......-----
.........|
........--
...--o| M2
...|....--
...------|
...........|---Vout
...........|
..........--
Vin--|| M1
..........--
...........|
.........----
.........VSS

and I know that the gain is Av = -gm1 * Rout and Rout = ro1 // (1/gm2) = 1/gm2
because ro1 is much bigger than 1/gm2 in general.

and this book says the gain is
Av = - (resistance in the drain) / (resistance in the source)
and resistance in the drain is 1/gm2 and resistance in the source is 1/gm1.

Now, I want to know how to find the resistances.

Why is the resistance in the source 1/gm1, not ro1 + (ro2 // 1/gm2)?
Why is the resistance in the drain 1/gm2, not 1/gm2 // ro1?