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US 5,514,972 AGranted
Voltage comparison circuit
AssigneeInternational Business Machines Corporation
InventorsMark K. DeMoor, Paul W. Graf, Jonathan J. Hurd
Life of this patent
Estimating the term…
Abstract
A circuit compares a difference between first and second voltages to a predetermined voltage. The circuit comprises an amplifier having first and second inputs. First and second capacitors are each coupled at one end to the first input of the amplifier. The first capacitor is charged with the first voltage and subsequently discharged. The second capacitor is charged with a first reference voltage and subsequently discharged. Third and fourth capacitors are each coupled at one end to the second input of the amplifier. The third capacitor is charged with the second voltage and subsequently discharged. The fourth capacitor is charged with a second reference voltage and subsequently discharged.
Claims25
A circuit for comparing a difference between first and second voltages to a predetermined voltage, said circuit comprising:
- an amplifier having first and second inputs;
- first and second capacitors each coupled at one end to said first input;
- means for charging said first capacitor with said first voltage during a first interval;
- means for charging said second capacitor with a first reference voltage during a second interval, said second interval following said first interval;
- third and fourth capacitors each coupled at one end to said second input;
- means for charging said third capacitor with said second voltage during said first interval;
- means for charging said fourth capacitor with a second reference voltage during said second interval;
- and
- switch means for connecting an output of said amplifier to said first input during an initial part of said first interval and disconnecting said output from said first input during a remainder of said first interval and during said second interval.
6 more elements
A circuit for comparing a difference between first and second voltages to a predetermined voltage, said circuit comprising:
- an amplifier having first and second inputs;
- first and second capacitors each coupled at one end to said first input;
- means for charging said first capacitor with said first voltage and subsequently discharging said first capacitor;
- means for charging said second capacitor with a first reference voltage and subsequently discharging said second capacitor;
- third and fourth capacitors each coupled at one end to said second input;
- means for charging said third capacitor with said second voltage and subsequently discharging said third capacitor;
- means for charging said fourth capacitor with a second reference voltage and subsequently discharging said fourth capacitor;
- and
- means for connecting a third reference voltage to said second input.
6 more elements
A circuit for comparing a difference between first and second voltages to a predetermined voltage, said circuit comprising:
- an amplifier having first and second inputs;
- first and second capacitors each coupled at one end to said first input;
- means for charging said first capacitor with said first voltage and subsequently discharging said first capacitor;
- means for charging said second capacitor with a first reference voltage and subsequently discharging said second capacitor;
- third and fourth capacitors each coupled at one end to said second input;
- means for charging said third capacitor with said second voltage and subsequently discharging said third capacitor;
- means for charging said fourth capacitor with a second reference voltage and subsequently discharging said fourth capacitor;
- timing means for causing said first and third capacitors to be charged by the respective charging means during a first interval;
- timing means for causing said second and fourth capacitors to be discharged during said first interval;
- switch means for connecting an output of said amplifier to said first input and;
- and
- timing means for causing said switch means to connect said output of said amplifier to said first input during at least part of said first interval.
9 more elements
A circuit for comparing a difference between first and second voltages to a predetermined voltage, said circuit comprising:
- an amplifier having first and second inputs;
- first and second capacitors each coupled at one end to said first input;
- means for charging said first capacitor with said first voltage and subsequently discharging said first capacitor;
- means for charging said second capacitor with a first reference voltage and subsequently discharging said second capacitor;
- third and fourth capacitors each coupled at one end to said second input;
- means for charging said third capacitor with said second voltage and subsequently discharging said third capacitor;
- means for charging said fourth capacitor with a second reference voltage and subsequently discharging said fourth capacitor;
- timing means for causing said first and third capacitors to be charged by the respective charging means during a first interval;
- timing means for causing said second and fourth capacitors to be discharged during said first interval;
- timing means for causing said second and fourth capacitors to be charged by the respective charging means during a second interval which follows said first interval;
- timing means for causing said first and third capacitors to be discharged during said second interval by the respective discharging means;
- and
- means for connecting a third reference voltage to said second input during a third interval within said first interval.
10 more elements
A circuit for comparing a difference between first and second voltages to a predetermined voltage, said circuit comprising:
- an amplifier having first and second inputs;
- first and second capacitors each coupled at one end to said first input;
- first and second switches each connected at one end to the other end of said first capacitor, said first switch connected at the other end to a port for receiving said first voltage, said second switch connected at the other end to ground;
- third and fourth switches each connected at one end to the other end of said second capacitor, said third switch connected at the other end to a port for receiving a first reference voltage, said fourth switch connected at the other end to ground;
- third and fourth capacitors each coupled at one end to said second input;
- fifth and sixth switches each connected at one end to the other end of said third capacitor, said fifth switch connected at the other end to a port for receiving said second voltage input, said sixth switch connected at the other end to ground;
- seventh and eighth switches each connected at one end to the other end of said fourth capacitor, said seventh switch connected at the other end to a port for receiving a second reference voltage, said eighth switch connected at the other end to ground;
- and
- a ninth switch connected between a third reference voltage and said second input.
6 more elements
A circuit for comparing a difference between first and second voltages to a predetermined voltage, said circuit comprising:
- an amplifier having first and second inputs;
- first and second capacitors each coupled at one end to said first input;
- first and second switches each connected at one end to the other end of said first capacitor, said first switch connected at the other end to a port for receiving said first voltage, said second switch connected at the other end to ground;
- third and fourth switches each connected at one end to the other end of said second capacitor, said third switch connected at the other end to a port for receiving a first reference voltage, said fourth switch connected at the other end to ground;
- third and fourth capacitors each coupled at one end to said second input;
- fifth and sixth switches each connected at one end to the other end of said third capacitor, said fifth switch connected at the other end to a port for receiving said second voltage input, said sixth switch connected at the other end to ground;
- seventh and eighth switches each connected at one end to the other end of said fourth capacitor, said seventh switch connected at the other end to a port for receiving a second reference voltage said eighth switch connected at the other end to ground;
- a ninth switch connected between an output of said amplifier and said first input of said amplifier;
- and
- a tenth switch connected between a third reference voltage and said second input of said amplifier.
7 more elements
A circuit for comparing a difference between first and second voltages to a predetermined voltage, said circuit comprising:
- an amplifier having first and second inputs;
- first and second capacitors each coupled at one end to said first input;
- first and second switches each connected at one end to the other end of said first capacitor, said first switch connected at the other end to a port for receiving said first voltage, said second switch connected at the other end to ground;
- third and fourth switches each connected at one end to the other end of said second capacitor, said third switch connected at the other end to a port for receiving a first reference voltage, said fourth switch connected at the other end to ground;
- third and fourth capacitors each coupled at one end to said second input;
- fifth and sixth switches each connected at one end to the other end of said third capacitor, said fifth switch connected at the other end to a port for receiving said second voltage input, said sixth switch connected at the other end to ground;
- and
- seventh and eighth switches each connected at one end to the other end of said fourth capacitor, said seventh switch connected at the other end to a port for receiving a second reference voltage, said eighth switch connected at the other end to ground;
- and
- wherein said predetermined voltage is the difference between said first and second reference voltages.
7 more elements
A circuit for comparing a difference between first and second voltages to a predetermined voltage, said circuit comprising:
- an amplifier having first and second inputs;
- first and second capacitors each coupled at one end to said first input;
- first and second switches each connected at one end to the other end of said first capacitor, said first switch connected at the other end to a port for receiving said first voltage, said second switch connected at the other end to ground;
- third and fourth switches each connected at one end to the other end of said second capacitor, said third switch connected at the other end to a port for receiving a first reference voltage, said fourth switch connected at the other end to ground;
- third and fourth capacitors each coupled at one end to said second input;
- fifth and sixth switches each connected at one end to the other end of said third capacitor, said fifth switch connected at the other end to a port for receiving said second voltage input, said sixth switch connected at the other end to ground;
- and
- seventh and eighth switches each connected at one end to the other end of said fourth capacitor, said seventh switch connected at the other end to a port for receiving a second reference voltage, said eighth switch connected at the other end to ground;
- and
- wherein each of said switches comprises three MOS transistors having their source drain paths in series with one another and the drain of one of the transistors is shorted to the source of the same transistor.
7 more elements
A circuit for comparing a difference between first and second voltages to a predetermined voltage, said circuit comprising:
- an amplifier having first and second inputs;
- a first capacitor coupled at one end to said first input;
- first switch means for charging said first capacitor with said first voltage during a first interval;
- a second capacitor coupled at one end to said second input;
- second switch means for charging said second capacitor with said second voltage during said first interval;
- and
- third switch means for connecting a third reference voltage to said second input during a part of said first interval.
4 more elements
A circuit for comparing a difference between first and second voltages to a predetermined voltage, said circuit comprising:
- an amplifier having first and second inputs;
- a first capacitor coupled at one end to said first input;
- first switch means for charging said first capacitor with said first voltage during a first interval;
- a second capacitor coupled at one end to said second input;
- second switch means for charging said second capacitor with said second voltage during said first interval;
- and
- third switch means for connecting an output of said amplifier to said first input during a part of said first interval.
4 more elements
Dependencies are inferred from the claim text.