Patent ID: 7026877

Claim:
An optical input preamplifier, comprising: a photodiode for converting an input optical signal into a photocurrent as an output current; means for pre-amplifying said output current from said photodiode, wherein said output current is pre-amplified to form a pre-amplifying current, wherein said pre-amplifying means comprises a feedback circuit creating a feedback signal in responsive to said output current from said photodiode to substantially form said pre-amplifying current, and an emitting follower electrically connected to said feedback circuit to output said pre-amplifying current therefrom; and an output circuit device converting said pre-amplifying current into an output signal, wherein said feedback circuit comprises a first transistor electrically connected with said photodiode and a second transistor electrically coupled with said first transistor such that when said output current from said photodiode is transmitted to said second transistor through said first transistor, said second transistor forms said feedback signal and transmits back to said first transistor so as to form said pre-amplifying current, wherein said first transistor is a NPN transistor and said second transistor is a PNP transistor, wherein said second transistor is electrically coupled with said first transistor to form a positive feedback circuit of said feedback circuit.