Low power digital signal isolator
First Claim
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1. A device for isolating a signal comprising:
- a. a differential pulse outputting means for receiving a first digital signal having a predetermined period and for producing differentiated pulses at a leading edge and at a trailing edge of said first digital signal;
b. a first photo-coupler having a phototransistor activated for a period of time which is substantially less than one half of said predetermined period of said first digital signal by said differentiated pulse produced at said leading edge;
c. a second photo-coupler having a phototransistor activated for a period of time which is substantially less than one half of said predetermined period of said first digital signal by said differentiated pulse produced at said trailing edge; and
d. a positive feedback means connected in push-pull fashion with said first and second photo-couplers for producing a second digital signal corresponding to said first digital signal.
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Abstract
A signal isolating device for an input digital signal has a first photo-coupler which is activated by the differential pulse produced at the leading edge of the digital signal and a second photo-coupler which is activated by the differential pulse produced at the trailing edge of the digital signal. A positive feedback system is connected in push-pull fashion with the photo-couplers for producing an output digital signal that corresponds to the input digital signal. The positive feedback system may be implemented by a buffer that includes a resistor for keeping the buffer in a stable state even when both of the photo-couplers are non-conductive.
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Citations
18 Claims
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1. A device for isolating a signal comprising:
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a. a differential pulse outputting means for receiving a first digital signal having a predetermined period and for producing differentiated pulses at a leading edge and at a trailing edge of said first digital signal; b. a first photo-coupler having a phototransistor activated for a period of time which is substantially less than one half of said predetermined period of said first digital signal by said differentiated pulse produced at said leading edge; c. a second photo-coupler having a phototransistor activated for a period of time which is substantially less than one half of said predetermined period of said first digital signal by said differentiated pulse produced at said trailing edge; and d. a positive feedback means connected in push-pull fashion with said first and second photo-couplers for producing a second digital signal corresponding to said first digital signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for isolating a signal comprising the steps of:
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a. producing differentiated pulses at a leading edge and at a trailing edge of a first digital signal, said first digital signal having a predetermined period; b. activating a first photo-coupler having a phototransistor for a period of time which is substantially less than half said predetermined period of said first digital signal by said differentiated pulse produced at said leading edge; c. activating a second photo-coupler having a phototransistor for a period of time which is substantially less than half said predetermined period of said first digital signal by said differentiated pulse produced at said trailing edge; and d. connecting a positive feedback means in push-pull fashion with said first and second photo-couplers for producing a second digital signal corresponding to said first digital signal. - View Dependent Claims (14, 15, 16, 17, 18)
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Specification