Latching comparator with hysteresis
First Claim
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1. A self latching comparator circuit having hysteresis, comprising:
- differential amplifier means having first and second inputs and first and second outputs, said first and second inputs being responsive to a differential signal applied thereacross;
first current mirror means coupled to said first and second outputs for producing a first predetermined input offset voltage in said differential amplifier means when said first current mirror means is activated, said first current mirror means including first transistor means;
second current mirror means coupled between said first and second outputs and a common node for producing a second predetermined input offset voltage in said differential amplifier means when said second current mirror means is activated, said second current mirror means being activated when the magnitude of said differential input signal incrementally exceeds said first predetermined input offset voltage in a positive sense for regeneratively inactivating said first current mirror means and said first current mirror means being activated when the magnitude of the differential input signal incrementally exceeds said second input offset voltage in a negative sense for regeneratively inactivating said second current mirror means, said second current mirror means including second transistor means;
first means for preventing said first transistor means from saturating when said first current mirror means is activated;
second means for preventing said second transistor means from saturating when said second current mirror means is activated; and
output circuit means coupled to said common node for causing a voltage level at an output thereof to switch between first and second output level states after said first and second current mirror means are respectively activated.
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Abstract
A self latching comparator circuit has upper and lower input offset voltages associated therewith to establish hysteresis in response to a differential input signal. The comparator circuit comprises a differential amplifier adapted to receive a differential input signal and first and second parallel current mirror circuits for producing upper and lower input offset voltages when each are respectively activated. Antisaturation means are provided for preventing the current mirror circuits from saturating. An output circuit is also provided which does not load the differential output and therefore provides for a well controlled hysteresis.
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9 Claims
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1. A self latching comparator circuit having hysteresis, comprising:
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differential amplifier means having first and second inputs and first and second outputs, said first and second inputs being responsive to a differential signal applied thereacross; first current mirror means coupled to said first and second outputs for producing a first predetermined input offset voltage in said differential amplifier means when said first current mirror means is activated, said first current mirror means including first transistor means; second current mirror means coupled between said first and second outputs and a common node for producing a second predetermined input offset voltage in said differential amplifier means when said second current mirror means is activated, said second current mirror means being activated when the magnitude of said differential input signal incrementally exceeds said first predetermined input offset voltage in a positive sense for regeneratively inactivating said first current mirror means and said first current mirror means being activated when the magnitude of the differential input signal incrementally exceeds said second input offset voltage in a negative sense for regeneratively inactivating said second current mirror means, said second current mirror means including second transistor means; first means for preventing said first transistor means from saturating when said first current mirror means is activated; second means for preventing said second transistor means from saturating when said second current mirror means is activated; and output circuit means coupled to said common node for causing a voltage level at an output thereof to switch between first and second output level states after said first and second current mirror means are respectively activated. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification