Abstract: A preamplifier includes a detector to detect an input optical power level and convert the detected input optical power level into an input current. The preamplifier also includes a transimpedance amplifier that provides a gain for the input current received from the detector. A dummy transimpedance amplifier is provided to supply a reference voltage. The dummy transimpedance amplifier has a structure similar to that of the transimpedance amplifier. A unity gain buffer is used to reduce the output impedance of the reference voltage and to output a bias voltage to both the transimpedance amplifier and the dummy transimpedance amplifier. This bias voltage can make the gate-controlled MOSFET working in its triode region, and the load resistance of the core amplifier can be easily controlled such that the gain and bandwidth of the core amplifier can be widely controlled. This results in the preamplifier having a high stability while its feedback resistor is controlled to achieve wide dynamic range.

Abstract: A preamplifier includes a detector to detect an input optical power level and convert the detected input optical power level into an input current. The preamplifier also includes a transimpedance amplifier that provides a gain for the input current received from the detector. A dummy transimpedance amplifier is provided to supply a reference voltage. The dummy transimpedance amplifier has a structure similar to that of the transimpedance amplifier. A unity gain buffer is used to reduce the output impedance of the reference voltage and to output a bias voltage to both the transimpedance amplifier and the dummy transimpedance amplifier. This bias voltage can make the gate-controlled MOSFET working in its triode region, and the load resistance of the core amplifier can be easily controlled such that the gain and bandwidth of the core amplifier can be widely controlled. This results in the preamplifier having a high stability while its feedback resistor is controlled to achieve wide dynamic range.