# US 7,411,468 B2 · Low voltage low-phase-noise oscillator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,411,468 B2 - Document ID: US7411468B2 - Status: Granted - Kind: B2 - Application number: 10/650,686 - Filed: 2003-08-29 - Published: 2005-03-03 - Granted: 2008-08-12 - Earliest claimed: 2003-08-29 - Assignees: The Hong Kong University of Science and Technology - Inventors: Howard Cam Luong; Ka-Chun Kwok - Web page: https://patentgrep.com/patent/US7411468B2 ## CPC - H03B 5/1228: {the amplifier comprising one or more field effect transistors} - H03B 5/1212: {the amplifier comprising a pair of transistors, wherein an output terminal of each being connected to an input terminal of the other, e.g. a cross coupled pair} - H03B 5/1215: {the current source or degeneration circuit being in common to both transistors of the pair, e.g. a cross-coupled long-tailed pair} - H03B 5/124: {the means comprising a voltage dependent capacitance} - H03B 5/1296: {the feedback circuit comprising a transformer} - H03B: GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS (generators adapted for electrophonic musical instruments G10H; masers or lasers H01S; generation of oscillations in plasma H05H) ## Abstract There is a disclosed an oscillator for generating a periodic signal, comprising a transistor and two electro-magnetically coupled inductors in positive feedback configuration, one of the inductors is connected to the drain or gate of the transistor, and the other being connected to the source to maintain the same phase of the two voltages at the two nodes. Two or more of such single ended oscillators can be connected together to form a differential oscillator, and the invention can be generalized by the use of any active device and not just transistors. ## Claims ### Claim 1 A single-ended oscillator configured to generate a periodic signal, comprising a transistor and two electro-magnetically coupled inductors in positive feedback configuration, wherein one of the said inductors is connected to a first terminal of the transistor and the other is connected to a second terminal of the transistor to maintain the same phase of respective voltages at the two connections, wherein the oscillator includes only parasitic capacitances. ### Claim 2 (depends on 1) An oscillator as claimed in claim 1 wherein the transistor is a PMOS, NMOS, PNP, or NPN transistor. ### Claim 3 (depends on 1) An oscillator as claimed in claim 1 wherein the transistor is configured to be a voltage-controlled current source. ### Claim 4 (depends on 1) An oscillator as claimed in claim 1 wherein the transistor is configured to be a current-controlled current source. ### Claim 5 (depends on 1) The singled-ended oscillator of claim 1, wherein the oscillator is configured to operate at a supply voltage that is substantially close to or less than the turn-on threshold voltage of the transistor. ### Claim 6 (depends on 1) A differential oscillator comprising two single-ended oscillators each configured as the single-ended oscillator of claim 1, wherein the two single-ended oscillators are configured to share a common bias current source. ### Claim 7 (depends on 5) A differential oscillator comprising two single-ended circuits each configured as the single-ended oscillator of claim 5, wherein said single-ended circuits are cross-coupled together either electrically or electro-magnetically for additional positive feedback. ### Claim 8 (depends on 1) A differential oscillator comprising two single-ended circuits each configured as the single-ended oscillator of claim 1, wherein said single-ended circuits are cross-coupled together either electrically or electro-magnetically for additional positive feedback. ### Claim 9 (depends on 8) A differential oscillator as claimed in claim 8 in which the two coupled inductor pairs are grouped together as a single multi-port transformer. ### Claim 10 (depends on 8) The differential oscillator as claimed in claim 8, further comprising two variable capacitors coupled between said single-ended circuits to tune the oscillators. ### Claim 11 (depends on 8) The differential oscillator as claimed in claim 8, wherein the first and second terminals of the transistors are drain and source nodes of the transistors. ### Claim 12 (depends on 11) A differential oscillator comprising two circuits each configured as the oscillator of claim 11, wherein said circuits are cross-coupled together either electrically or electro-magnetically to provide additional positive feedback. ### Claim 13 (depends on 12) The differential oscillator of claim 12, wherein the two oscillators are configured to be coupled to a common bias current source. ### Claim 14 (depends on 8) The differential oscillator as claimed in claim 8, further comprising two variable capacitors coupled between said single-ended circuits to tune the oscillators. ### Claim 15 A multiple-output oscillator comprising a plurality of single ended circuits each of which comprises a transistor and two inductors with one of the inductors coupled to a first terminal of the transistor and the other coupled to a second terminal of the transistor, wherein the inductors in each of the single ended circuits are electro-magnetically coupled with inductors in another single ended circuit to form pairs of inductors in a ring configuration, and the multiple-output oscillator includes only parasitic capacitances. ### Claim 16 (depends on 15) A multiple-output oscillator of claim 15, wherein the oscillator is configured to operates at a supply voltage that is substantially close to or less than the turn-on threshold voltage of the transistor. ### Claim 17 (depends on 15) A multiple-output oscillator of claim 15, wherein any two or more inductors are grouped together as a single multiple-port transformer. ### Claim 18 An oscillator for generating a periodic signal, comprising: a transistor and two electro-magnetically coupled inductors configured in a positive feedback configuration void of any capacitor responsive to presence of parasitic capacitance, to generate the periodic signal, wherein one of the said inductors is coupled to a first terminal of the transistor and the other is coupled to a second terminal of the transistor to maintain respective voltages across the two couplings at substantially the same phase. ### Claim 19 (depends on 18) The oscillator as claimed in claim 18 wherein the transistor is configured to act as a selected one of a voltage-controlled current source or a current-controlled current source.