| 摘要 |
PURPOSE:To obtain a gain controlling circuit having linear control characteristics, by connecting one end of a fixed resistor and an MOS transistor (TR) as an output terminal, and giving a DC-biased input signal to the other terminal and a control signal to the gate. CONSTITUTION:The gate of a TRQ1 is connected to the drain as a fixed resistor, and a DC-biased signal is given to the drain of a TRQ2. A control voltage Vhk of a negative weight is given to the gate of the TRQ2. The TRs have the same threshold value as that of input gates of CCD. Then, the cutoff voltage of a gain controlling circuit consisting of the CCD can be set slightly lower than the cutoff voltage of the circuit, the CCD is cut off earlier, no excessive DC charge is poured to or flowed out of the transfer channel, allowing to effectively use the dynamic range of the transfer channel of CCD. |
