| 摘要 |
PROBLEM TO BE SOLVED: To provide a method which does not use a DC/DC converter to widen the dynamic range of a signal amplifying circuit for photodetection for a bar code reader built-in pen type handy terminal. SOLUTION: A DAC and an ADC built in a CPU are connected to an amplifying circuit and an amplified signal while fed back to the ADC is monitored and has its level adjusted by the DAC to prevent the amplified signal from exceeding a source voltage. Consequently, the need to widen the dynamic range of the amplifying circuit is eliminated and then a DC/DC converter is reduced to make the mount area, thereby making the terminal small-sized and lightweight. |
