I am trying to get into understanding of current mirrors, amplifiers and other basic electronic blocks, and I have come across this a lot, but I couldn't find an explanation how that works anywhere (maybe I was Googling the wrong words). For example, concerning this basic differential input circuit:
How can there be any current flowing through the MOSFETs, when the Gate is grounded? I was under an impression that MOSFETs (the standard ones) conduct Drain to Source (or vice versa) current only when there is a Gate to Source voltage applied (and an inversion layer forms the channel and so on).
Futhermore I came across that you can bias a MOSFET in pretty much the same way, by placing a current source to the Source terminal. How does that work? I thought you can bias only by setting a Gate-Source voltage. Can a MOSFET be opened by forcing the current between the Drain and Source?
Man, I am confused.