| 摘要 |
PURPOSE:To apply a binarizing circuit as the circuit of a bar code reader and to obtain a proper binarized output all the time by correcting a reference voltage to the amplitude center side with the binarized output and delaying the time when a signal voltage becomes equal to the reference voltage. CONSTITUTION:A high feedback resistance Rf is connected between the output terminal of a comparator and the summing point of a capacitor C1 and reverse parallel diodes D1 and D2l. When the signal voltage Vin becomes close to the reference voltage Vref, the signal voltage Vin drops and the diodes D1 and D2 become high in resistance and the reference voltage Vref drops more than before because of the presence of the feedback resistance Rf, so the time when Vin=Vref is obtained is delayed slightly and eventually. When the signal voltage Vin rises to make the diodes D1 and D2 high in resistance and the signal voltage Vin becomes close to the reference voltage Vref, on the other hand, the reference voltage Vref rises more than before and the time when Vin-Vref is obtained is delayed slightly. Consequently, the level of the reference level can be uniformed regardless of the amplitude of the signal voltage is large or small, so the more accurate binarized output is obtained. |
