Patent ID: 7206521
Filing Date: 2007-04-17
Classification: H04B

Abstract:
1. An optical receiver having a pre-amplifier for converting a current signal outputted from an optical detector to a voltage signal and a signal level detecting device for providing an LOS (loss of signal) signal and a reset signal from the output of the pre-amplifier, said signal level detecting device comprising: a first capacitor for receiving the output from the pre-amplifier; first and second transistors each comprising an emitter, a collector, and a base, wherein the emitter of the first transistor and the collector of the second transistor are connected to the output of the pre-amplifier, and the base of each transistor is connected to the collector of each, respective transistor; a third transistor having a collector that is connected to the collector of the first transistor and an emitter that is connected to the collector of the second transistor; a common emitter circuit having first and second resistors and detecting the level of a signal inputted from the collector of the third transistor, wherein the first resistor is connected to the emitter of the third transistor and the second resistor is connected to the collector of the third transistor; a fourth transistor connected to said common emitter circuit and turns on when an output signal is present; a second capacitor connected to the fourth transistor to charge a predetermined voltage when the fourth transistor turns on; and a fifth transistor connected to the fourth transistor to output a low signal when the fourth transistor turns on.