| 摘要 |
A laser driver utilizes a difference amplifier circuit to produce a servo signal, and a tracking circuit for storing a digital approximation of the servo signal. During a write mode of operation, the tracking circuit produces a stored tracking signal which does not change. This tracking signal is used as the baseline current to which write pulses are added during the write mode. The digital approximation of the servo signal is input to a digital-to-analog converter to produce the tracking signal which does not drop over time. During a read mode of operation the tracking circuit incrementally updates the stored approximation of the servo signal. The laser driver also incorporates a correction mechanism in the difference amplifier circuit to prevent the servo signal from dropping too low during write mode operations, and eliminates large transients during the switch from write mode to read mode. |
