Patent ID: 7358818
Filing Date: 2008-04-15
Classification: H03F,H03G

Abstract:
1. An optical receiver for receiving optical signals each having different transmission speed and outputting electrical signals corresponding to optical signals, said optical receiver comprising: a light-receiving device for generating signal currents corresponding to said optical signals; a pre-amplifier having an input terminal, an output terminal and a control terminal, said input terminal being connected to one terminal of said light-receiving device for inputting said signal current, and said output terminal outputting voltage signals corresponding to said current signals converted by said pre-amplifier, said pre-amplifier including an amplifying circuit and a trans-impedance connected in parallel to said amplifying circuit and disposed between said input and output terminals, said amplifying circuit having a transistor and a load circuit connected to said transistor, said transistor being connected to said input terminal and said load circuit including at least one resistor and at least a first circuit unit having a first switching device and a resistor connected in parallel with each other, said trans-impedance including at least one resistor and a second circuit unit having a second switching device and a resistor connected in parallel with each other; a main amplifier for amplifying said voltage signals and outputting said electrical signals, said main amplifier being connected to said output terminal of said pre-amplifier; and a control circuit for outputting said control signal in accordance with said transmission speed, wherein said pre-amplifier varies a gain, a frequency bandwidth and a noise characteristic thereof by controlling said first and second switching devices with said control signal depending on said transmission speed.