Variable Gain Amplifier Using CM Offset Regulators to Cut Power
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Solution Overview
Problem
Traditional variable gain amplifiers in high-speed serial communication systems face significant power consumption due to common mode voltage mismatches, which are typically addressed using Inter-Digital Analog Converters (IDACs that modulate current through termination resistors, resulting in substantial power overhead.
Innovation Solution
A variable gain amplifier design featuring independent common mode nodes and regulators for each differential signal, eliminating the need for IDACs by generating a net common mode offset to replace current source offsets, thereby reducing power consumption and simplifying the design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If IDACs are used to offset common mode voltage mismatches by modulating current through termination resistors, then common mode offset correction is achieved, but power consumption increases significantly
Solution Approach 1:
The patent extracts and eliminates the IDAC components from the circuit, replacing them with a voltage-based common mode offset correction mechanism. This removes the unnecessary current modulation through termination resistors while maintaining the essential function of common mode offset correction, thereby significantly reducing power consumption.
Solution Approach 2:
The patent substitutes the current-based IDAC mechanism with a voltage-based regulation system. Instead of using Inter-Digital Analog Converters to modulate currents, the invention employs voltage regulators to directly control and correct common mode voltages, replacing a complex current modulation system with a simpler voltage control approach that consumes less power.
2Reliability
If IDAC-based current modulation is used to correct common mode voltage mismatches, then offset correction is achieved, but device complexity increases
Solution Approach 1:
The patent removes the IDAC components and associated current modulation circuitry from the design. By extracting these complex elements and replacing them with simpler voltage regulator circuits, the invention maintains common mode offset correction functionality while significantly reducing overall device complexity.
Solution Approach 2:
The patent changes the fundamental operating parameter from current modulation (IDAC approach) to voltage regulation. This parameter change simplifies the circuit architecture by eliminating the need for complex current control mechanisms while achieving the same common mode offset correction through more straightforward voltage control.
Data Source
AI summary
A variable gain amplifier includes a first common mode (CM) node configured to receive a first differential signal of a pair of differential signals. A first regulator couples to the first CM node, the first regulator being configured to generate a first CM offset. A second CM node is configured to receive a second differential signal of the pair of differential signals. A second regulator couples to the second CM node, the second regulator being configured to generate a second CM offset. In one embodiment, the first CM offset and the second CM offset together comprise a net CM offset, the net CM offset being configured to replace a current source net offset.