Circuits and methods including dual gate field effect transistors
First Claim
1. A method, comprising:
- coupling source and drain terminals of a first dual gate field effect transistor to a first voltage;
coupling a primary gate of the first dual gate field effect transistor to a second voltage that is different than the first voltage; and
coupling a secondary gate of the first dual gate field effect transistor to a third voltage that is different than the first voltage and the second voltage,wherein coupling the primary gate to the second voltage includes coupling the primary gate to an output of an operational amplifier.
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Abstract
Dual gate FD-SOI transistors are used as MOSFET capacitors to replace passive well capacitors in analog microcircuits. Use of the dual gate FD-SOI devices helps to reduce unstable oscillations and improve circuit performance. A thick buried oxide layer within the substrate of an FD-SOI transistor forms a capacitive dielectric that can sustain high operating voltages in the range of 1.2 V-3.3 V, above the transistor threshold voltage. A secondary gate in the FD-SOI transistor is used to create a channel from the back side so that even when the bias voltage on the first gate is small, the effective capacitance remains higher. The capacitance of the buried oxide layer is further utilized as a decoupling capacitor between supply and ground. In one example, a dual gate PMOS FD-SOI transistor is coupled to an operational amplifier and a high voltage output driver to produce a precision-controlled voltage reference generator. In another example, two dual gate PMOS and one dual gate NMOS FD-SOI transistor are coupled to a charge pump, a phase frequency detector, and a current-controlled oscillator to produce a high-performance phase locked loop circuit in which the decoupling capacitor footprint is smaller, in comparison to the conventional usage of passive well capacitance.
47 Citations
19 Claims
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1. A method, comprising:
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coupling source and drain terminals of a first dual gate field effect transistor to a first voltage; coupling a primary gate of the first dual gate field effect transistor to a second voltage that is different than the first voltage; and coupling a secondary gate of the first dual gate field effect transistor to a third voltage that is different than the first voltage and the second voltage, wherein coupling the primary gate to the second voltage includes coupling the primary gate to an output of an operational amplifier. - View Dependent Claims (2, 3, 4)
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5. A method, comprising:
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coupling source and drain terminals of a first dual gate field effect transistor to a first voltage; coupling a primary gate of the first dual gate field effect transistor to a second voltage that is different than the first voltage; coupling a secondary gate of the first dual gate field effect transistor to a third voltage that is different than the first voltage and the second voltage; coupling source and drain terminals of a second dual gate field effect transistor to the first voltage; coupling a primary gate of the second dual gate field effect transistor to the second voltage; and coupling a secondary gate of the second dual gate field effect transistor to the third voltage, wherein coupling the primary gates of the first and second dual gate field effect transistors to the second voltage includes coupling the primary gates to an output of a first stage of a charge pump phase locked loop circuit, the first stage operable to output the second voltage based on a received input signal at an input frequency. - View Dependent Claims (6, 7, 8, 9)
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10. A method, comprising:
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forming a capacitive dual gate field effect transistor in an active layer of a silicon-on-insulator (SOI) substrate having a buried oxide layer overlying a doped region, the capacitive transistor including source and drain regions having substantially vertical profiles that are oriented perpendicular to the buried oxide layer, the transistor having a primary gate, and a secondary gate in the doped region; forming a front side contact to the doped region of the transistor; coupling the source and drain regions to a first voltage; coupling the primary gate to an output of an operational amplifier, the operational amplifier configured to output a second voltage that is different than the first voltage; and coupling the secondary gate to a third voltage that is different than the first voltage and the second voltage. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A method, comprising:
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coupling a supply voltage to source and drain terminals of a dual gate PMOS transistor formed on a doped substrate that includes a buried oxide layer; applying a bias voltage to a primary gate of the dual gate PMOS transistor to control current in a channel region between the source and drain terminals; grounding the doped substrate via a secondary gate; and operating the dual gate PMOS transistor as an integrated capacitor, wherein applying the bias voltage includes outputting the bias voltage from an output terminal of an operational amplifier. - View Dependent Claims (18, 19)
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Specification