Patent ID: 7738519

Claim:
A laser driver circuit including a laser APC circuit receiving a monitor current indicative of the average optical output power of a laser diode and providing a bias adjust signal for adjusting a bias current for the laser diode, the laser APC circuit comprising: a first non-linear impedance circuit receiving the monitor current and generating a first voltage using a first non-linear current-to-voltage transfer function; a second non-linear impedance circuit receiving a reference current and generating a second voltage, the second non-linear impedance circuit being implemented using the first non-linear current-to-voltage transfer function or a scaled version of the first non-linear current-to-voltage transfer function; and a comparator for comparing the first voltage with the second voltage, the comparator providing the bias adjust signal indicative of the difference between the first voltage and the second voltage, wherein the first non-linear current-to-voltage transfer function has a high resistance portion at a low current range and a low resistance portion at a high current range for increasing the dynamic range of the current-to-voltage conversion.