| 摘要 |
PROBLEM TO BE SOLVED: To make a sample-and-hold circuit follow immediately a rise of input to actuate and to make the output level of the circuit hold accurately for a long time even if a mark rate on input data is greatly fluctuated by a method wherein a light intensity control device is provided with an amplifier, which receives the output of the sample-and-hold circuit and controls the luminous level of a light-emitting element which corresponds to marks or spaces of input. SOLUTION: In the case where a sample-and-hold control signal is significant in a first sample-and-hold control circuit 15, that is, in the case where a light output is '1' in mark, a current is led from a first sample-and-hold circuit 12 in the circuit 15 and the circuit 12 is put in a sample mode. That is, the circuit 12 abruptly follows an input. In the case where the light output is '0' in space, the lead-in of the current is stopped from the circuit 12 and the circuit 12 is put in a hold mode. The time constant of the circuit 12 at that time is generally set in a large time constant and the output of the circuit 12 is held constant for a long time. |
