Patent ID: 6586918
Filing Date: 2003-07-01
Classification: G05F,H01S

Abstract:
A current mirror circuit of a laser driver circuit, the current mirror circuit comprising a current mirror, said current mirror comprising:first and second mirror transistors each having a base electrode and an emitter electrode; a resistive element R1 coupled between said base electrodes; and a first emitter resistor R2 and a second emitter resistor R3 coupled, respectively, to the emitter electrodes of the first and second mirror transistors; wherein the resistive element is coupled between said base electrodes such that, in use, base leakage current to the first transistor from a current supply causes a voltage drop across the resistive element, wherein the voltage drop acts to boost a voltage through the emitter resistor of the second mirror transistor, thereby to boost, in use, output current provided by the second mirror transistor to the laser driver circuit; and the emitter resistors R2 and R3 have resistances relationship of the form: R3=1N&it;R2and one of:R1=(N+1)R2 and R1R2=(N+1)&it;(1+NVTR2&it;Iout)where:N is an overall gain of the current mirror; and VT=kT/q, where k is Boltzmann's constant, q is charge and T is the absolute temperature.