| 摘要 |
PURPOSE:To fully utilize integrated circuit technologies for the production of a photodetecting circuit excellent in response in a high-frequency environment at a required output level by a method wherein the output DC bias of each stage is made to be the DC bias most suitable for the stage. CONSTITUTION:AMP-1 is a negative feedback amplifier circuit provided with a feedback resistor Rf. Q1 and Q2 constitute an inverter amplifier and its DC bias voltage is set at an optimal value, and a voltage VL at a level shift section, constituted of Q3 and Q4 and SBD (Schottky barrier diode) is made to match said optimal value. Further, by a buffer amplifier constituted of Q5 and Q6 and provided with a constant current source involving Q4, the output DC voltage, that is, the DC bias voltage to be applied to an inverter amplifier constituted of Q7 and Q8 of AMP-2 of the next stage, is made to match the optimal DC bias voltage of the inverter amplifier constituted of Q1 and Q2, and the output impedance is lowered for the suppression of reduction in the high-frequency response capability ascribable to the input capacity of AMP-2 and the like.
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