Phase noise reduction in LC-VCO
AssigneeGlobalfoundries Inc.
InventorsAnthony R. Bonaccio, Zhenrong Jin, Ram Kelkar, Anjali R. Malladi, Ramana M. Malladi
Life of this patent
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Abstract
An approach for a transconductance cell for use in a voltage controlled oscillator (VCO) is provided. The transconductance cell includes a first NFET stack connected in series to a first PFET stack. The transconductance cell includes a second NFET stack connected in series to a second PFET stack. The first NFET stack and the first PFET stack are cross-coupled to the second NFET stack and the second PFET stack. The first NFET stack and the second NFET stack are connected to a tail node. The first PFET stack and the second PFET stack are connected to a power supply node.
Claims20
A transconductance cell for use in a voltage controlled oscillator (VCO), comprising:
- a first NFET stack connected in series to a first PFET stack;
- and
- a second NFET stack connected in series to a second PFET stack,
- wherein the first NFET stack and the first PFET stack are cross-coupled to the second NFET stack and the second PFET stack;
- the first NFET stack and the second NFET stack are connected to a tail node;
- and
- the first PFET stack and the second PFET stack are connected to a power supply node;
- wherein the first NFET stack comprises a first NFET and a second NFET;
- the second NFET stack comprises a third NFET and a fourth NFET;
- the first PFET stack comprises a first PFET and a second PFET;
- and
- the second PFET stack comprises a third PFET and a fourth PFET.
A transconductance cell for use in a voltage controlled oscillator (VCO), comprising:
- a first NFET stack connected in series to a first PFET stack;
- and
- a second NFET stack connected in series to a second PFET stack,
- wherein the first NFET stack and the first PFET stack are cross-coupled to the second NFET stack and the second PFET stack;
- the first NFET stack and the second NFET stack are connected to a tail node;
- and
- the first PFET stack and the second PFET stack are connected to a power supply node,
- wherein transistors of the first NFET stack, the first PFET stack, the second NFET stack, and the second PFET stack are sized to provide a same transconductance and a reduced phase noise relative to another transconductance cell that includes only non-stacked transistors.
A voltage controlled oscillator, comprising:
- an inductor connected between a first node and a second node;
- at least one varactor connected between the first node and the second node;
- and
- a transconductance cell connected between the first node and the second node, wherein the transconductance cell comprises:
- a first NFET set connected in series to a first PFET set;
- and
- a second NFET set connected in series to a second PFET set,
- wherein the first NFET set and the first PFET set are cross-coupled to the second NFET set and the second PFET set;
- the first NFET set and the second NFET set are connected to a tail node that is selectively switched to ground;
- the first PFET set and the second PFET set are connected to a power supply node;
- and
- at least one of:
- the first NFET set and the second NFET set each comprises a pair of stacked NFETs, and the first PFET set and the second PFET set each comprises a pair of stacked PFETs.
A method, comprising:
- fabricating a transconductance cell for use in a voltage controlled oscillator (VCO), wherein the transconductance cell comprises:
- a first NFET stack connected in series to a first PFET stack;
- and
- a second NFET stack connected in series to a second PFET stack,
- wherein the first NFET stack and the first PFET stack are cross-coupled to the second NFET stack and the second PFET stack;
- the first NFET stack and the second NFET stack are connected to a tail node that is selectively connected to ground by a switch;
- and
- the first PFET stack and the second PFET stack are connected to a power supply node that supplies a rail voltage.
Dependencies are inferred from the claim text.