Optical receiver with improved dynamic range
AGC circuit including a precision voltage clamp and method Patent #: 4718119
ApplicationNo. 494077 filed on 03/15/1990
US Classes:330/284, Having attenuation means in signal transmission path250/214A, Amplifier type250/214AG, Automatic gain control330/308Including atomic particle or radiant energy impinging on a semiconductor
ExaminersPrimary: Mullins, James B.
Attorney, Agent or Firm
Foreign Patent References
International ClassesH03F 003/08
AbstractAn optical receiver circuit for an incoming optical signal having a variable power level includes an optical detector for receiving the optical signal and generating a current therefrom which varies with the optical signal power level. The current so generated is applied to a transimpedance amplifier. An automatic gain control (AGC) drive circuit is connected around the amplifier thereby increasing its dynamic range. The AGC drive circuit drives a FET which has one side thereof connected to the transimpedance amplifier for shunting current from the input thereof. A negative feedback circuit comprising an amplifier is connected across the FET, which comprises the resistive feedback element, thus reducing the FET resistance by a factor of 1+T, where T is the feedback circuit loop gain.