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US 7,889,006 B1Granted
dB-linear process-independent variable gain amplifier
AssigneeMaxim Integrated Products, Inc.
InventorMark Jones
Life of this patent
Estimating the term…
Abstract
An amplifier is provided with continuously-variable analog control that exhibits a highly linear gain control curve in db/volts, while preserving high dynamic range, low third order distortion, and low noise. This amplifier has a control mechanism that preserves a varied linear or log linear curve over a wide range and is inherently insensitive to process variations thereby allowing more accurate gain control and higher signal fidelity for amplifying high dynamic range signals.
Claims21
A gate voltage control circuit comprising:
- a first MOSFET having a gate, a source and a drain;
- a feedback loop comprising:
- a feedback transistor;
- a first resistance being connected in series between an emitter of the feedback transistor and the drain of the first MOSFET;
- a feedback resistor configured to provide a linear current at a collector of the feedback transistor, the feedback element connected with the collector of the feedback transistor;
- and
- an op amp that receives a feedback voltage originated at a node between the feedback resistor and the collector of the feedback transistor, the op amp provides an output that is used as a gate control voltage, the gate control voltage is received at the gate of the first MOSFET, the gate control voltage modulates the transconductance of the combination of first MOSFET and the first resistance;
- and
- a second MOSFET having a gate, a source and a drain, the second MOSFET matched to the first MOSFET, the gate of the second MOSFET connected to receive the gate control voltage.
6 more elements
A variable gain amplifier comprising:
- a transconductance amplifier, the transconductance amplifier comprising:
- a first transconductor circuit comprising a first MOSFET;
- and
- a second transconductor circuit comprising a second MOSFET, the second transconductor circuit being connected in parallel with the first transconductor circuit;
- a first gate voltage control circuit having a first gate control voltage output connected to a gate of the first MOSFET, the first gate voltage control circuit comprising:
- a third MOSFET having a gate, a source and a drain;
- a first feedback loop comprising:
- a first feedback transistor;
- a first resistance being connected in series between an emitter of the first feedback transistor and the drain of the third MOSFET;
- a first feedback resistor connected in series with a collector of the feedback transistor;
- and
- a first op amp that receives a first feedback voltage originated at a first node between the first feedback resistor and the collector of the first feedback transistor, the first op amp provides a first output that is used as a first gate control voltage, the first gate control voltage received at a gate of the first MOSFET, the first gate control voltage connected to control a transconductance of the combination of the third MOSFET and the first resistance;
- and
- a second gate voltage control circuit having a second gate control voltage output connected to the base of the second MOSFET, the second gate voltage control circuit comprising:
- a fourth MOSFET having a gate, a source and a drain;
- and
- a second feedback loop comprising:
- a second feedback transistor;
- a second resistance being connected in series between an emitter of the second feedback transistor and the drain of the fourth MOSFET;
- a second feedback element connected in series with a collector of the feedback transistor;
- and
- a second op amp that receives a second feedback voltage originated at a second node between the second feedback resistor and the collector of the second feedback transistor, the second op amp provides a second output that is used as a second gate control voltage, the second gate control voltage is received at a gate of the second MOSFET, the second gate control voltage connected to control a transconductance of the combination of the fourth MOSFET and the second resistance.
19 more elements
A log linear variable gain amplifier comprising:
- a plurality of transconductance circuits connected in parallel, each transconductance circuit comprising a first MOSFET, each first MOSFET comprising a gate;
- amplifier circuitry having a gain determined by the transconductance between two nodes, the two nodes being connected in parallel with the plurality of transconductor circuits;
- and
- a plurality of gate voltage generator circuits, each gate voltage generator circuit comprising:
- a control voltage input for receiving a control voltage, the control voltage having a control voltage range;
- a second MOSFET, each second MOSFET being matched to a different first MOSFET in the plurality of transconductance circuits;
- and
- a feedback loop that includes the second MOSFET, the feedback loop being adapted to produce a gate control voltage output that is a log linear transconductance variation of the second MOSFET over the control voltage range, the gate control voltage output being connected to the gate the matched first MOSFET such that the amplifier circuitry produces a log linear gain for a predetermined portion of the control voltage range.
5 more elements
Dependencies are inferred from the claim text.