Comparator with signal related adaptive bias
First Claim
1. In a voltage responsive comparator, said comparator including a differential amplifier having means for supplying a source of operating current, differential inputs, and an output that constitutes said comparator output, means for coupling a reference voltage to one of said differential inputs, and means for coupling a voltage source to the other of said differential inputs, said comparator ordinarily producing an error when coupled to voltage sources of limited current capability, the improvement comprising:
- means for controlling said operating current in proportion to the current available from said voltage source; and
means for biasing at least one input of said differential amplifier in proportion to said current available from said voltage source whereby said differential amplifier responds to said voltage source at current levels substantially below those useful in comparators without said improvement.
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Abstract
A high gain differential amplifier is used in a comparator circuit. A bias control circuit is coupled to the differential amplifier so that its current is a multiple of the signal current. Input stage current drain is reduced by biasing the stage with a current source operating at a fraction equal to the signal current multiple. When so configured, the amplifier current and bias are related to the input current in a manner that permits good response to large signals and extended range response to small signals to give an extended dynamic range.
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Citations
7 Claims
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1. In a voltage responsive comparator, said comparator including a differential amplifier having means for supplying a source of operating current, differential inputs, and an output that constitutes said comparator output, means for coupling a reference voltage to one of said differential inputs, and means for coupling a voltage source to the other of said differential inputs, said comparator ordinarily producing an error when coupled to voltage sources of limited current capability, the improvement comprising:
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means for controlling said operating current in proportion to the current available from said voltage source; and means for biasing at least one input of said differential amplifier in proportion to said current available from said voltage source whereby said differential amplifier responds to said voltage source at current levels substantially below those useful in comparators without said improvement. - View Dependent Claims (2, 3, 4)
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5. A voltage comparator having inverting and noninverting input terminals, an output terminal, and a current control terminal, said comparator comprising:
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a differential amplifier having means for coupling to a source of operating current, a pair of inputs coupled respectively to said inverting and noninverting input terminals, a common mode output, and a differential output; means coupled to said control terminal for controlling said operating current in said differential amplifier; means for developing a second current in proportion to said operating current; means for combining said differential output and said second current to provide a signal at said output terminal of said comparator. - View Dependent Claims (6, 7)
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Specification