| 摘要 |
PURPOSE:To obtain a linear analog signal from a digital signal, by providing a means for changing the ratio of high to low level per one period of the digital signal, a means for integrating the digital signal, and a means for resetting an integration value. CONSTITUTION:When a digital signal inputted to an input terminal A is in a high level, the signal is integrated by a capacitor 14 via a diode 12. When the digital signal is in a low level, since the diode 12 is turned off, the potential of the capacitor 12 is kept as it is. When a reset signal B is inputted to an analog switch 15, the switch 15 is conductive at each occasion, the charge charged in the capacitor 14 is discharged and the potential is brought to zero. The potential inputted to an operational amplifier 13 is equal to the potential charged to the capacitor 14 when the digital signal is in a high level and is proportional to the duty ratio of the digital signal. Thus, the analog output voltage is proportional to the duty ratio. |
