Differential comparator with differential threshold for local area networks or the like
AssigneeAT&T Corp.
InventorsFrancisco J. Fernandez, Robert H. Leonowich
Life of this patent
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Abstract
A master-slave differential comparator having a threshold value. The master section controls the threshold value of the slave section. The slave section is controlled by bias currents therein to matching same in the master section. The bias currents are substantially determined by fixed biases applied to the master section, the difference in biases being substantially equal to the threshold value of the comparator.
Claims12
A comparator having two inputs and a differential threshold value, disposed in an integrated circuit, having a first (slave) section, the first section being CHARACTERIZED BY:
- a first differential pair of transistors (31) having a common output, two inputs, and two outputs, the inputs coupling to the inputs of the comparator;
- a first variable current source (34) coupling to the common output of the first differential pair;
- a first bilateral current mirror (32) coupling to the outputs of the first differential pair;
- a first amplifier stage having an output and coupling to one output of the first differential pair, the output being an output of the comparator;
- wherein the differential threshold value of the comparator is substantially determined by the current passed by the current source.
A comparator having two inputs, an output, and a differential threshold value, the comparator having an first (slave) section, the first section being CHARACTERIZED BY:
- a first differential pair of transistors (13), having two inputs and two outputs, the inputs coupling to the corresponding inputs of the comparator;
- a first amplifier stage (11.sub.L), having a variable bias (17.sub.L), an input coupling to an output of the first differential pair, and an Output coupling to the output of the comparator;
- wherein the differential threshold value of the comparator is substantially determined by the amount of bias in the amplifier stage.
In an integrated circuit, a comparator having two inputs for comparing a signal on the inputs to a differential threshold value, and an output, CHARACTERIZED BY:
- a master section (3) having:
- a first differential pair of transistors (23) with two inputs, two outputs, and a common output, the inputs connected to fixed biases having voltages differing by a predetermined voltage corresponding to the differential threshold voltage;
- and
- means (21,28) coupled to the two outputs of the first pair of transistors, for producing a control signal (TSET) proportional to the predetermined voltage;
- and a slave section (2) having:
- a second differential pair of transistors (13) with two inputs, two outputs, and a common output, the inputs coupling to the inputs of the comparator;
- and
- amplifying means (11.sub.L, 12.sub.L) including a variable current source (17.sub.L) for providing bias currents in the amplifier means in response to the control signal, coupling to at least one of the outputs of the second pair of transistors and having an output coupling to the output of the comparator, for setting the differential threshold value of the comparator in response to the control signal.
Dependencies are inferred from the claim text.