Isn't it the case here in this common gate arragement ? Drain current variations are converted to voltage ones using the 1K5 drain resistors...Look at Nelson's I/V. It is probably the same type of thingie. Just put a BJT where he uses a MOSFET.
MOSFETs are transconductance devices. Current in, voltage out. It works, but I prefer BJTs. Transresistance types: current in, current out.
Then convert the current to a voltage with........a resistor