Current Mirror vs. Current Source

Please explain to me the difference between a normal current source and a current mirror(using Mosfets or BJTs).. What advantage does a current mirror offer over a normal current source. Why cant we directly use the reference current used in current mirrors for biasing or other purposes. is it because of lower output impedance that a Mosfet offers and thus lesser dependence of output current on load..??

Current Mirror vs. Current Source

Please explain the difference between a normal Current Mirror vs. Current Source or BJTs).. What advantage does a current mirror offer over a normal current source. Why cant we directly use the reference current used in current mirrors for biasing or other purposes. is it because of lower output impedance that a Mosfet offers and thus lesser dependence of output current on load..??