Polaroid Corporation

Bryan A Santarelli

Marc T Thompson

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

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Haverhill, MA, United States of America

Bryan A Santarelli