Biasing analog circuit : Beta multiplier or Resistor bias

[engrvip]

Is it a good idea to use on chip resistor to provide biasing currents to the current mirrors in analog circuit ?

Or should self biasing "beta multiplier" ckt be used to generate this biasing current always ????


Also what are the disadvantages of using the biasing resistor external to the chip to generate bias current inside the chip , in this way I can vary resistor to change baising current inside the chip?