Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
It works as a resistor, so if a current flows through it, a voltage is generated. This voltage is applied to the other MOS gate and another current is generated.
You can obtain a desired current by changing the sizes of the transistors.
See Design of Analog CMOS ICs (Razavi).