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US 5,859,606 AGranted
Interpolation circuit for digital-to-analog converter
AssigneeLinear Technology Corporation
InventorsVictor Paul Schrader, James Lee Brubaker
Life of this patent
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AssigneeLinear Technology Corporation
InventorsVictor Paul Schrader, James Lee Brubaker
Estimating the term…
A voltage interpolation circuit for a digital-to-analog converter comprises a differential amplifier with composite input devices, each of which is composed of multiple active subtransistors. Interpolation is effected between a first voltage and a second voltage by selectively connecting the gates of the active subtransistors in one of the composite devices to either the first voltage or the second voltage. Each active subtransistor operates in conjunction with a voltage-controlled degeneration subtransistor to form a functional subtransistor pair. Using the nonlinear conductance characteristic of MOS devices operated in the triode region, the transconductance of each functional subtransistor pair is modulated in such a way as to be made relatively insensitive to changes in effective gate-to-source voltage V.sub.GS ', so that the interpolation circuit produces equally sized interpolated voltage steps at an analog output.
A composite input circuit for use in an interpolation circuit that interpolates between a first voltage and a second voltage in response to a digital control word to produce an analog output voltage, the interpolation circuit having a first terminal for supplying the first voltage, a second terminal for supplying the second voltage, a differential transconductance stage having a first half and having a second half formed of at least one transistor having a control gate, a source, and a drain, a current source having an output to which the source of the at least one transistor in the second half of the differential transconductance stage is coupled, an output terminal for supplying the analog output voltage, and a feedback path for coupling the output terminal to the control gate of the at least one transistor in the second half of the differential transconductance stage, the composite input circuit comprising:
A composite input circuit for use in an interpolation circuit that interpolates between a first voltage and a second voltage in response to a digital control word to produce an analog output voltage, the interpolation circuit having a first terminal for supplying the first voltage, a second terminal for supplying the second voltage, a differential transconductance stage having a first half and having a second half formed of at least one transistor having a control gate, a source, and a drain, a current source having an output to which the source of the at least one transistor in the second half of the differential transconductance stage is coupled, an output terminal for supplying the analog output voltage, and a feedback path for coupling the output terminal to the control gate of the at least one transistor in the second half of the differential transconductance stage, the composite input circuit comprising:
Dependencies are inferred from the claim text.