Low-voltage, current-folded signal modulators and methods
AssigneeLinear Technology Corporation
InventorMin Z. Zou
Life of this patent
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Abstract
A low voltage, current-folded signal modulator that reduces distortion in the output signal is provided. The signal modulator has a differential amplifier that receives a first input signal and converts it to a current, a current amplifier that has a low impedance input and provides an amplified current signal, and a differential pair circuit that receives a second input signal and modulates the amplified current signal by the second signal.
Claims50
A circuit that generates an output signal at an output node proportional to a first signal at a first signal node modulated by a second signal at a second signal node, the circuit comprising:
- a transconductance amplifier circuit comprising an input terminal coupled to the first signal node;
- a current mirror circuit coupled to an output of the transconductance amplifier, the current mirror circuit comprising a feedback circuit;
- and
- a differential pair circuit comprising a first input terminal coupled to the second signal node, a second input terminal coupled to an output of the current mirror circuit, and an output terminal coupled to the output node.
A method for generating an output signal proportional to a first voltage signal modulated by a second signal, the method comprising:
- converting the first voltage signal to a first current signal using a transconductance amplifier;
- amplifying the first current signal to provide a second current signal using a current mirror circuit having a feedback circuit;
- and
- multiplying the second current signal with the second signal using a differential pair circuit.
A method for generating an output signal proportional to a first time varying voltage signal modulated by a second time varying signal, the method comprising:
- converting the first time varying voltage signal to a first current signal;
- folding the first current signal to produce a current folded signal;
- providing negative feedback to the current folded signal to limit distortion in the current folded signal;
- amplifying the current folded signal to produce an amplified current signal;
- and
- multiplying the amplified current signal by the second time varying signal to produce the output signal.
An improved signal modulator circuit that generates an output signal at an output node proportional to a first signal at a first signal node modulated by a second signal at a second signal node, the signal modulator having (1) a transconductance amplifier circuit coupled to the first signal node, and (2) a differential pair circuit coupled to the second signal node and the output node, the improvement comprising:
- a current amplifier circuit comprising a current mirror circuit coupled to an output of the transconductance amplifier and the differential pair, the current mirror circuit comprising a feedback circuit coupled to the output of the transconductance amplifier.
Dependencies are inferred from the claim text.