WinChai
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First of all thanks a lot for the reply! I've been stuck on this for quite a while now, so I'd be glad if there was anybody who had the same experience, but I wasn't expecting an author of the book!
Okay, now back to the problem.
Problem1: I see what you mean by Fig. 12, eq (32) being almost constant with bias current and Fig. 15, eq (41) being almost linear with current. However it can be seen that eq (32) is not a function of bias current or tank resistance, we would expect it to be constant with bias current. eq (41) however is inversely dependent on the resistance of the tank. And since from the simulation example in the book the I*R product is kept constant, increasing the current will automatically decrease the tank resistance making the gate gain automatically increase with bias current. This makes me feel like the equivalent of calculating the transconductance gain of an amplifier, then calculating the voltage gain of the amplifier and saying that they are some how separate gain. Is there something wrong with this logic?
In other words while this is obvious from the equations, what I don't understand is how eq (32) and eq (41) can be said to be separate gains since it seems that just by replacing the current noise in (32) with a Vn/R eq (32) becomes eq (41), which, like I said in the initial post, make them seem like the same gain values measured with different units, (V/I) VS (V/V) ie. just scaled differently. Is there something wrong with this logic? For example is it not valid to replace "In" by Vn/R? And if so why not? This is what I don't understand. I mean while they maybe derived separately, they seem to refer to the same gain.
So the way I saw it is that when you calculate the tank gain, you are also calculating the gate gain as well, however, just with different units (just replacing In with Vn/R). Is there something wrong with this logic?
Problem 2: I will try out the method that you have suggested and see what happens.
Thanks for the reply! I actually have some other points I don't understand about the book, but maybe later.
Win
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