| 摘要 |
PURPOSE:To reduce the saturation degree of a transformer impedance type amplifier and to obtain an output signal having no distortion from a large input light current by forming a by-pass route when a difference between the output voltage of the amplifier and the input terminal voltage of a constant current load is prescribed value or more to prevent an output voltage from being dropped. CONSTITUTION:The drain and source of an FET Q5 are respectively connected to the input and output terminals of the amplifier 2. The gate of an FET Q6 is connected to the output terminal of the amplifier 2 to obtain an output signal VOUT from the gate. A constant current load consisting of an FET Q7 whose source and gate are short-circuited is connected between the source of the FET Q6 to be a source follower and a ground and voltage VDD is applied to the drain of the FET Q6. The FET Q5 is set up so as to be turned on when the input light current iPD exceed a prescribed value. Consequently, the saturation degree of the amplifier 2 can be suppressed without advancing the drop of the output voltage VOUT to a prescribed value or less. |
