A current mirror includes a serially connected diode-connected transistor of a
first conductivity type, a saturated (fully-on) transistor of a second conductivity
type, and a current source for providing a reference current. A gate voltage generated
by the diode-connected transistor in response to the reference current is provided
to the gate of a matching transistor. This causes the matching transistor to mirror
the reference current. Meanwhile, an output transistor cascoded with the matching
transistor is gate-coupled to the junction between the saturated transistor and
the current source. This allows the output transistor to provide an output voltage
swing from one supply voltage to two saturation voltage drops from the second supply
voltage. Meanwhile, the cascode configuration gives the current mirror a high output impedance.