| 摘要 |
PURPOSE:To eliminate temperature dependency on an inverted level of a comparator circuit, to attain small size and less effect due to temperature by providing a current mirror circuit to a comparator circuit and connecting a collector of a couple of transistors(TRs) being components of an input stage to a collector of a couple of TRs being components of the current mirror circuit respectively. CONSTITUTION:A current mirror circuit 10 to compare optical current outputs of photodetectors 1, 2 and to eliminate the effect of temperature fluctuation is provided to a comparator circuit 7 in an optical current amplifier provided with the plural photodetectors 1, 2, logarithmic amplifiers 3, 4 amplifying logarithmically the optical current outputs from the photodetectors 1, 2 and the comparator circuit 7 comparing the output voltage with a reference voltage. Then collectors of a couple of TRs Q1, Q2 being components of the input stage of the comparator circuit 7 are connected respectively to collectors of a couple of TRs Q3, Q4 being components the current mirror circuit 10 and different emitter areas of the TRs Q3, Q4 are differentiated. Thus, the optical current amplifier is realized with small size and low cost, in which the temperature compensation is sufficiently implemented. |
