Logarithmic amplifier, and image read-out apparatus using the sa

Details Logarithmic amplifier, and image read-out apparatus using the sa Logarithmic amplifier, and image read-out apparatus using the sa

1990-01-18

1991-04-02

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controlled circuit

250214L.327.2, 330 51, H01J 4014

Patent

active

050049062

ABSTRACT:
A logarithmic amplifier comprises an amplifier provided with a feedback circuit, a logarithmic conversion device in the feedback circuit, an oscillation preventing circuit which is provided with a capacitor connected in parallel with the logarithmic conversion device, and a control circuit. The control circuit controls the oscillation preventing circuit in accordance with the current fed into the logarithmic amplifier, so that the amount of certain components in the output from the amplifier, which components are fed back to an input terminal of the amplifier through the oscillation preventing circuit, decreases as the current fed into the logarithmic amplifier becomes smaller. An image read-out apparatus comprises a photoelectric detector which detects light from a recording medium, which light is emitted by the recording medium when it is scanned, and the logarithmic amplifier into which the output current generated by the photoelectric detector is fed. An image having good sharpness is thereby obtained.

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