CAPACITOR SWITCHING CIRCUIT
First Claim
1. A capacitance switching element, comprising:
- a first capacitor;
a second capacitor;
a first transistor comprising a first gate, a first source, and a first drain;
a second transistor comprising a second gate, a second source, and a second drain, wherein the first transistor and the second transistor are coupled in series between the first capacitor and the second capacitor;
a first resistor connecting the first gate to a first control signal;
a second resistor connecting the second gate to the first control signal;
a third resistor connecting the second drain to a second control signal;
a fourth resistor connecting the first source to the second control signal; and
a fifth resistor connecting the second source and the first drain to the second control signal;
wherein the second control signal is a level-shifted compliment of the first control signal.
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Accused Products
Abstract
A capacitance switching element includes first and second capacitors connected in series by transistors. The gates of the transistors are biased by a first signal through one set of resistors, and the sources and drains are biased by a second signal through a second set of resistors. The signals are level-shifted and may be complimentary. To turn the element ON, the first signal may be set to VDD and the second signal may be set to zero. To turn the element OFF, the first signal may be set to a multiple of VDD/2 and the second signal may be set to the multiple plus one of VDD/2. When the element is used in an oscillator tuning circuit, the voltage stress on the transistors is reduced and the transistors may be fabricated with thin oxide. The oscillator may be used in a transceiver of a cellular access terminal.
26 Citations
26 Claims
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1. A capacitance switching element, comprising:
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a first capacitor; a second capacitor; a first transistor comprising a first gate, a first source, and a first drain; a second transistor comprising a second gate, a second source, and a second drain, wherein the first transistor and the second transistor are coupled in series between the first capacitor and the second capacitor; a first resistor connecting the first gate to a first control signal; a second resistor connecting the second gate to the first control signal; a third resistor connecting the second drain to a second control signal; a fourth resistor connecting the first source to the second control signal; and a fifth resistor connecting the second source and the first drain to the second control signal; wherein the second control signal is a level-shifted compliment of the first control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A capacitance switching element, comprising:
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a first capacitor; a second capacitor; a first transistor comprising a first gate, a first source, and a first drain; a second transistor comprising a second gate, a second source, and a second drain; a third transistor comprising a third gate, a third source, and a third gate, wherein the first transistor, the second transistor, and the third transistor are coupled in series between the first capacitor and the second capacitor; a first resistor connecting the first gate to a first control signal; a second resistor connecting the second gate to the first control signal; a third resistor connecting the third gate to the first control signal; a fourth resistor connecting the third drain to a second control signal; a fifth resistor connecting the third source and the second drain to the second control signal; a sixth resistor connecting the second source and the first drain to the second control signal; and a seventh resistor connecting the first source to the second control signal; wherein; the capacitance switching element is configured to operate from a power supply configured to deliver a supply voltage potential (VDD) and ground potential; the first control signal is pulled up to substantially the VDD; and the second control signal switches between (1) substantially the ground potential to connect the first capacitor to the second capacitor, and (2) substantially one and a half times the VDD potential to disconnect the first capacitor from the second capacitor. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A capacitance switching element, comprising:
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a first capacitor; a second capacitor; a plurality of n transistors, n being at least three, each transistor of the plurality of transistors comprising a gate, a source, and a drain, wherein the transistors are coupled in series between the first capacitor and the second capacitor; a first plurality of resistors connecting the gates of the transistors to a first control signal; a second plurality of resistors connecting the drains and sources of the transistors to a second control signal; wherein; the capacitance switching element is configured to operate from a power supply configured to deliver a supply voltage potential (VDD) and a ground potential; the first control signal switches between substantially the VDD and substantially ((n−
1)/2) times the VDD; andthe second control signal switches between substantially the ground potential and substantially (n/2) times the VDD potential. - View Dependent Claims (19)
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20. A capacitance switching element, comprising:
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a first capacitor; a second capacitor; and a means for selectively coupling the first capacitor and the second capacitor in series and reducing transistor voltage stress.
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21. A method of switching capacitance, the method comprising:
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providing a first capacitor and a second capacitor; providing a first transistor and a second transistor coupled in series between the first capacitor and the second capacitor; biasing gates of the first and second transistors at substantially a supply voltage VDD and biasing sources and drains of the first and second transistors at substantially ground potential to connect the first capacitor to the second capacitor; and biasing the gates of the first and second transistors at substantially one half of the VDD and biasing the sources and drains of the first and second transistors at substantially the VDD to disconnect the first capacitor from the second capacitor. - View Dependent Claims (22, 23)
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24. A method of switching capacitance, the method comprising:
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providing a first capacitor and a second capacitor; providing a plurality of n transistors, n being at least three, wherein the transistors of the plurality of transistors are coupled in series between the first capacitor and the second capacitor; biasing gates of each transistor of the plurality of transistors at substantially a supply voltage VDD and biasing sources and drains of said each transistor at substantially ground potential to connect the first capacitor to the second capacitor; and biasing the gates at substantially ((n−
1)/2) times VDD and biasing the sources and drains at substantially (n/2) times VDD to disconnect the first capacitor from the second capacitor. - View Dependent Claims (25, 26)
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Specification