| 摘要 |
PURPOSE:To prevent the malfunction of a waveform shaper by enlarging a protection action against surging by providing the resistor of a required value connected in series to a clamp diode and the waveform shaper which waveform- shapes an input signal and outputs a digital signal and is positioned at the following stage of the protection resistor. CONSTITUTION:When a radio wave trouble noise is impressed, at a point A, a waveform becomes such the waveform that the radio wave trouble noise is superimposed on an original input signal waveform. In contrast to this, at the input terminal B of a filter IC 10, a noise (f) filtered by a time constant determined by the protection resistor 1 and a capacitor 7 is superimposed on an input signal (e). At that time, simultaneously with this, asymmetry is caused in the waveform at the time of Hi by the influence of DC restoration by a power supply side clamp diode 2. However, an average level (h) at the time of the input signal Hi in the case the radio wave trouble noise is received becomes higher compared with that in the past, and becomes close to supply voltage VDD. Namely, the influence of the DC restoration by this clamp diode 2 is reduced by the action of a power supply side resistor 3, and the malfunction can be prevented. |
