Comparator circuit
First Claim
1. A comparator circuit constructed with MOSFETs of a LOCOS-drain structure formed on a P-type silicon substrate, the comparator circuit comprising:
- a first P-channel MOSFET of the LOCOS-drain structure having a source connected to a first power supply, which supplies a first supply voltage, through a first resistance element and a gate to which a reference voltage is applied;
a second P-channel MOSFET of the LOCOS-drain structure having a source connected to the first power supply through a second resistance element and a gate to which an input signal voltage is applied;
a current mirror circuit connected between drains of the first and the second P-channel MOSFETs and a ground;
a comparison operation unit having a reference voltage input terminal and a comparison voltage input terminal, which are connected to the drains of the first and the second P-channel MOSFETs, respectively, and comparing the input signal voltage and the reference voltage, with power being provided from a second power supply, which supplies a second supply voltage lower than the first supply voltage of the first power supply; and
voltage clamping means, disposed on a reference voltage input terminal side of the comparison operation unit, for performing a clamp operation when a potential of the terminal tends to rise above a predetermined level.
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Accused Products
Abstract
A reference voltage and an input signal voltage are applied to gates of FETs each equipped with a LOCOS-drain structure, respectively, and currents according to the voltages are made to flow from a power supply voltage Vbat to drain sides through resistors and sources, respectively. The currents are made to flow in FETs to be converted to voltages. Then, both voltages are compared in a comparator. When a potential of a reference voltage input terminal in the comparator that operates with power provided by a power supply Vcc tends to rise above a predetermined level, a FET is turned on and clamps the voltage so as to suppress its potential rise.
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Citations
6 Claims
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1. A comparator circuit constructed with MOSFETs of a LOCOS-drain structure formed on a P-type silicon substrate, the comparator circuit comprising:
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a first P-channel MOSFET of the LOCOS-drain structure having a source connected to a first power supply, which supplies a first supply voltage, through a first resistance element and a gate to which a reference voltage is applied; a second P-channel MOSFET of the LOCOS-drain structure having a source connected to the first power supply through a second resistance element and a gate to which an input signal voltage is applied; a current mirror circuit connected between drains of the first and the second P-channel MOSFETs and a ground; a comparison operation unit having a reference voltage input terminal and a comparison voltage input terminal, which are connected to the drains of the first and the second P-channel MOSFETs, respectively, and comparing the input signal voltage and the reference voltage, with power being provided from a second power supply, which supplies a second supply voltage lower than the first supply voltage of the first power supply; and voltage clamping means, disposed on a reference voltage input terminal side of the comparison operation unit, for performing a clamp operation when a potential of the terminal tends to rise above a predetermined level. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification