I have a question about this page from this book - Design of Analog CMOS Integrated Circuits.
The author isn't being very clear on distinguishing what is small-signal and what is large-signal. In the point marked (1), a step is applied at Vin,CM. Is this small-signal or large-signal. From the point marked (2), I believe it should be a small-signal step since the author is using g_m for the gain. However, in the point marked (3), he is stating that bias points are affected.
I'm confused. Is the Vin,CM step supposed to be treated as small-signal or large-signal? If it is large-signal, then g_m cannot be assumed to be fixed?
Or is the author just using this to gain intuition and not being rigorous.