PULSE WIDTH CONVERTING CIRCUIT

PURPOSE:To improve remarkably noise resistance by constituting the titled circuit so that a reference voltage of a comparator is changed in synchronizing with ON/OFF period of a pulse signal. CONSTITUTION:A value of a resistor r3' is increased, a (+) input terminal voltage of a comparator OP2 is decreased, a diode D is inserted between the said terminal and a collector of a transistor TR1 to increase the (+) input terminal voltage of the comparator OP2 only when an input pulse width TIN is at a low leve. In taking a difference between the (+) input terminal voltage and the (-) input terminal voltage of the comparator OP2 as vc'' and taking a period of voltage rise by the vc'' due to the charging of a capacitor C as Td3, a difference vc' between a maximum value of the (-) input voltage and the (+) input voltage is increased up to K/(K-1) times, and when K=1.5 is adopted, vc''=3vc' and when K=1.2, the relation of vc''=6vc' is obtained, then the noise resistance is improved considerably.