They differ in a lot of parameters. (e.g. zero output impedance vs high output impedance)
Thanks for your comments. I think your comment is the key point of my questions. May I ask one more question? Sorry for endless following questions..
Regarding your comments, a beginner like myself may have a stupid thinking: (beyond the circuits...) it is common sense that if there is an ideal model, then a simple example would (try to) have similar values to those of an ideal model, even though a simple example cannot have the exact same values as those of an ideal model.
Basically, I don't understand the reason why we study an ideal amp model, then.
In my stupid opinion, even simple voltage amp may be trying to have similar values, not even close to those of the ideal voltage amp model, because the output impedance in my previous example is a very important parameter.
In the same book written by Dr. Razavi, there are many other amplifier examples, which are not too much simple amp that I mentioned in my previous question. Some of them have large output impedance and small input impedance. So, I'm wondering if those amplifiers have an opposite magnitude of Rout or Rin to that of an ideal amp, simply because those example amplifiers are poorly designed for education purpose for this book.
-s55