| 摘要 |
PROBLEM TO BE SOLVED: To demodulate an FSK signal or the like with stable and high sensitivity and linearity by means of correcting a manufacture nonuniformity and aged changes due to it by providing a means for charging/discharging an electric load as against a storing means for storing and holding a threshold based on the comparison result of a voltage value with a reference voltage value. SOLUTION: A prescribed inclination is given to the rise or fall of a rectangular pulse by an integrating means consisting of constant current sources 20a and 20b and capacitors 22a and 22b, it is compared with a threshold, a pulse stream with a pulse width based on the comparison result is smoothed, a voltage value corresponding to the frequency of the rectangular pulse is obtained, the voltage value is compared with a reference voltage value and the threshold is controlled based on the result. When the voltage value is larger than the prescribed reference value, an electric charge is discharged from the capacitor 16 storing and holding the threshold. When the voltage value is smaller than the prescribed reference voltage value, the electric charge is charged to the capacitor 16 storing and holding the threshold.
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