MOS current-steering circuits
A current mirror may consist of many MOSFET current sources This circuit is particularly useful in integrated circuit design, where one resistor R is used to make multiple current sources the current mirror simply ensures that the gate to source voltages of each transistor is equal to the gate to source voltage of the reference
· Current sink: pulls a dc current from a circuit
· Current source: pushes a dc current into a circuit
· All transistors should be operated in saturation
· Current mismatch exists for a finite VA (channel-length modulation)
From the standpoint of integrated circuit design, we can change the value of K by modifying the MOSFET channel width-to-length ratio (W/L) for each transistor.