CMOS comparator output circuit with high gain and hysteresis
First Claim
Patent Images
1. A circuit which produces a binary output voltage at an output in response to a time varying input signal, the circuit comprising:
- a first current mirror having a transistor that is series coupled with the output and produces a first current at the output in response to the input signal;
a second current mirror having a transistor that is series coupled with the output and produces a second current at the output in response to a bias current, the first and the second currents producing the binary output voltage having a state determined by relative magnitudes of the first current and the second current; and
a bias circuit including a bias current source, a switchable current source, and a switch coupled between the switchable current source and the second current mirror for switching the switchable current source so as to provide the bias current at one of a first value and a second value in response to the state of the binary output voltage.
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Abstract
A comparator circuit (100) produces a binary output voltage at an output (109) in response to a time varying input signal received at an input (108). The comparator circuit includes an output circuit (106) having a first current mirror (202), a second current mirror (204), a bias circuit (206) and a helping current source (208). Bias currents are applied in response to the state of the output voltage at the output to increase the gain and the hysteresis of the output circuit.
49 Citations
13 Claims
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1. A circuit which produces a binary output voltage at an output in response to a time varying input signal, the circuit comprising:
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a first current mirror having a transistor that is series coupled with the output and produces a first current at the output in response to the input signal; a second current mirror having a transistor that is series coupled with the output and produces a second current at the output in response to a bias current, the first and the second currents producing the binary output voltage having a state determined by relative magnitudes of the first current and the second current; and a bias circuit including a bias current source, a switchable current source, and a switch coupled between the switchable current source and the second current mirror for switching the switchable current source so as to provide the bias current at one of a first value and a second value in response to the state of the binary output voltage. - View Dependent Claims (2, 3, 4, 5)
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6. A circuit which produces a binary output voltage in response to an input current, the circuit comprising:
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a first current mirror configured to receive the input current and produce a first polarity current; a second current mirror configured to receive a bias current and produce a second polarity current, the first current mirror and the second current mirror each having a transistor series coupled with an output of the circuit to produce the binary output voltage; and a bias circuit coupled to the second current mirror and producing the bias current at one of a first magnitude and a second magnitude responsive to state of the binary output voltage, the bias circuit including a bias current source which produces a first portion of the bias current, a switchable current source which produces a second portion of the bias current, and a switch to switch in the switchable current source when the binary output voltage has a predetermined level so as to combine the first and second portions of the bias current. - View Dependent Claims (7)
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8. A comparator comprising:
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an input stage which compares a time varying input voltage and a reference voltage and produces an intermediate voltage in response to the comparison; a converter coupled to the input stage which produces an input current in response to the intermediate voltage; an input circuit coupled to the converter and configured to receive the input current; a comparing circuit coupled to the input circuit, the comparing circuit establishes an output voltage at a first value when the input current exceeds a first predetermined threshold of a bias current and at a second value when the input current exceeds a second predetermined threshold of the bias current; and a bias circuit coupled to the comparing circuit, the bias circuit varies the bias current in response to the output voltage to establish hysteresis in the comparator. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification