Browse Prior Art Database

Edge-Detection Circuit

IP.com Disclosure Number: IPCOM000060220D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Marple, WP: AUTHOR [+2]

Abstract

Edge-detection circuits serve to identify the rising edge or falling edge on the input waveform. Problems have arisen in the prior art with regard to input noise which can occasionally rise above the threshold for detection of the edge-detected waveform. A solution to this problem is provided by the invention disclosed herein, by allowing the following voltage of the edge-detected to be of lesser magnitude than the rising voltage of the edge-detected signal. This can be seen with reference to waveforms B and C. Waveform B is the edge-detected signal in its uncorrected state, wherein a positive threshold and a negative threshold for detection of the edge- detected signal is provided.

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Edge-Detection Circuit

Edge-detection circuits serve to identify the rising edge or falling edge on the input waveform. Problems have arisen in the prior art with regard to input noise which can occasionally rise above the threshold for detection of the edge- detected waveform. A solution to this problem is provided by the invention disclosed herein, by allowing the following voltage of the edge-detected to be of lesser magnitude than the rising voltage of the edge-detected signal. This can be seen with reference to waveforms B and C. Waveform B is the edge-detected signal in its uncorrected state, wherein a positive threshold and a negative threshold for detection of the edge- detected signal is provided. A problem arises in the noise which would also accompany the edge-detected signal and whose spikes could be easily confused for a true edge-detected signal. The improvement of the invention is shown in waveform diagram C wherein the input signal starts at the amplitude 1 and when the edge of the input waveform A is detected, the edge-detected signal in waveform C rises at 2 to an amplitude at 3. Based upon the circuit elements of the edge-detecting circuit, after a duration delta T, the edge-detected circuit in waveform C begins to fall at 4. The improvement in the invention is limiting the magnitude of that fall so that the amplitude at 5 occurs which is substantially more positive than the negative threshold for detection of edge-detected signals in the circuit. As time goes on and a negative-going edge is detected for the input signal at waveform A, the edge detector outputs the detected waveform C which goes negative at 6 to an amplitude at 7 for a duration of delta T. Then the waveform goes positive at 8, but its magnitude of voltage swing is diminished so that it stops at 1', substantially more negative than the positive threshold for detection of edge- detected signals in the circuit. Fig. 1 is an illustration of one form of an edge- detection circuit which provides...