| 摘要 |
PURPOSE:To obtain a data identifying device enabled to reduce the resolution of an analog-digital (A/D) converter to a comparatively small value by providing an envelope detector and a subtractor. CONSTITUTION:The envelope detector 6 detects and outputs a lower side envelope of an input signal. The subtractor 7 subtracts the output of the detector 6 from an input signal and outputs the subtracted value. Thereby, the output of the subtractor 7 is obtained by fixing the lower side envelope of the input signal on a fixed voltage and inputted to the A/D converter 1 to identify the data. The lower side envelope is detected from an input signal buffered by a buffer 8 with a specific time constant through a diode 9, a capacitor 11 and a resistor 12. A diode 10 and a resistor 13 operate so as to offset voltage drop generated by the diode 9 at the detection of the envelope, so that the subtractor 7 fixes the flower side envelope of the input signal near '0' volt to output the envelope.
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