A current source is an electronic circuit that delivers or
absorbs an electric current which is independent of the voltage across it. A
current source is the dual of a voltage source. The term constant-current sink
is sometimes used for sources fed from a negative voltage supply. Figure 1
shows the schematic symbol for an ideal current source, driving a resistor
load. There are two types. An independent current source sources or sinks a
constant current. A dependent current source delivers a current which is
proportional to some other voltage or current in the circuit
