Waveform-shaping circuit and a data-transmitting apparatus using such a circuit
First Claim
1. A waveform-shaping circuit, which level-discriminates an input signal so as to carry out a waveform-shaping operation by using the higher of the two values, that is, a first threshold value that is selected as a peak value of a first signal that varies in response to the input signal and a second threshold value that is selected as the average of the input signal, comprising:
- a peak-hold circuit for finding the peak value of the first signal;
an average-value calculating circuit for finding the average of the input signal; and
a capacitor that is commonly used for a holding operation in the peak-hold circuit as well as for an integrating operation in the average-value calculation circuit,wherein;
the direction of currents to be supplied to the capacitor from the peak-hold circuit and the average-value calculating circuit is limited only to a first direction and the waveform-shaping circuit is further provided with a bypass means, installed in parallel with the capacitor, for allowing current to flow in a direction reversed to the first direction.
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Accused Products
Abstract
In an infrared data-receiving circuit wherein an output electric current of a photodiode is current-to-voltage converted by a preamplifier and, after having been amplified by an amplification circuit, is subjected to a waveform-shaping operation in a comparator by using a predetermined threshold value, the threshold voltage, upon receipt of a low signal voltage, is set at the average value Vav that has been formed by two LPFs and, upon receipt of a high signal voltage, is also set at a shift value that has been obtained by allowing the voltage, which has been generated by shifting of a level shift circuit, to be sampled by a peak-hold circuit constituted of a differential amplifier. Thus, the apparatus is allowed to deal with a wide dynamic range. Moreover, in this arrangement, a single capacitor may be commonly used for an integrating operation in the LPFs and for a holding operation in the peak-hold circuit so as to provide a simple construction that is preferably applied to an integrated circuit. Consequently, in the infrared data-receiving circuit that uses the output from the photodiode by subjecting it to the waveform-shaping operation, it becomes possible to deal with a wide range of level differences by using a simple construction.
45 Citations
9 Claims
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1. A waveform-shaping circuit, which level-discriminates an input signal so as to carry out a waveform-shaping operation by using the higher of the two values, that is, a first threshold value that is selected as a peak value of a first signal that varies in response to the input signal and a second threshold value that is selected as the average of the input signal, comprising:
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a peak-hold circuit for finding the peak value of the first signal; an average-value calculating circuit for finding the average of the input signal; and a capacitor that is commonly used for a holding operation in the peak-hold circuit as well as for an integrating operation in the average-value calculation circuit, wherein;
the direction of currents to be supplied to the capacitor from the peak-hold circuit and the average-value calculating circuit is limited only to a first direction and the waveform-shaping circuit is further provided with a bypass means, installed in parallel with the capacitor, for allowing current to flow in a direction reversed to the first direction. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An infrared data-transmitting apparatus for receiving data through infrared light that is spatially transmitted, comprising:
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a photoelectric transfer element for converting the spatially transmitted infrared light into an electric signal; and a waveform-shaping circuit, which level-discriminates the input signal so as to carry out a waveform-shaping operation by using the higher of the two values, that is, a first threshold value that is selected as a peak value of a first signal that varies in response to the input signal derived from the electric signal and a second threshold value that is selected as the average of the input signal, comprising; a peak-hold circuit for finding the peak value of the first signal; an average-value calculating circuit for finding the average of the input signal; and a capacitor that is commonly used for a holding operation in the peak-hold circuit as well as for an integrating operation in the average-value calculation circuit, wherein;
the direction of currents to be supplied to the capacitor from the peak-hold circuit and the average-value calculating circuit is limited only to a first direction and the waveform-shaping circuit is further provided with a bypass means, installed in parallel with the capacitor, for allowing current to flow in a direction reversed to the first direction. - View Dependent Claims (9)
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Specification