| 摘要 |
<p>A laser driver circuit applies pulses of current to a laser diode (10) to activate the diode to emit pulses of radiation suitable for operation of a laser printer (16). A field-effect transistor (12) (FET) is serially connected with the laser diode (10) and with a feedback resistor (32) for applying the current pulses, the feedback resistor (32) serving as a source of a feedback signal indicative of the magnitude of current flow. A photodetector (54) senses radiation outputted by the laser diode (10) and emits an optical feedback signal representative of radiated power of the laser diode. A combiner circuit (40) responsive to an input digital command signal, combines the current feedback signal and the optical feedback signal with the command signal to generate a drive signal for activating the FET (12). The combiner circuit (40) includes an input section in which a current source powers a differential amplifier operating in a switching mode in response to the command signal, a driver section (84) wherein a current source powers a differential amplifier operating in a linear mode and connecting between the input section and the FET (12), and a threshold section (76) connected to the input section for establishing a threshold current level in the drive signal which activates the FET (12).</p> |
