| 摘要 |
PURPOSE:To simplify a temperature compensation circuit portion in a logarithmic compression circuit by shifting the level of the logarithmic compression output with a non-linear element and a constant current source for non-inversion amplification. CONSTITUTION:A voltage proportional to the logarithmic value of the intensity of incident light through a light receiving element SPC is generated from an operational amplifier A1 composing a compression means connected to a feedback diode D1. The voltage is shifted in the level with a diode D2 of a non- linear element direct connected to a constant current circuit CS2 and applied to a non-inversion input terminal with a large input impedance of an operational amplifier A3 for non-inversion processing. A resistance R1 for determining amplification characteristic whose resistance value is proportional to the difference between the absolute temperature and the reference absolute temperature is connected to the non-inversion input terminal of the amplifier A3. This eliminates any operational amplifier for temperature compensation between the amplifiers A1 and A3 to simplify the temperature compensation circuit portion within the logarithmic circuit and thus reduces the number of pins in the corresponding monolithic IC to achieve a smaller size. |
