Variable Gain Amplifier With Time-Domain Calibration and Positive Feedback
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Solution Overview
Problem
Traditional precision amplifiers face challenges in achieving precise gain in nanometer-scale devices due to reduced intrinsic gain and increased sensitivity to process variation, while dynamic amplifiers suffer from limited maximum achievable gain and increased non-linearity, especially in pipelined SAR ADCs, which require large open-loop gains and consume static power.
Innovation Solution
A variable gain amplifier utilizing positive feedback and time-domain calibration, which operates in an open-loop configuration with a digital timing loop to tune the gain, incorporating an integration phase for reduced noise and offset and a regeneration phase for high-speed amplification, allowing for flexible trade-offs between noise, linearity, and speed, and consuming no static power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional closed-loop amplifiers are used to achieve precise gain, then measurement precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The amplification process is segmented into two distinct phases: an integration phase that accumulates charge on capacitors to achieve precise gain, and a regeneration phase that restores signal levels. This segmentation allows each phase to be optimized independently, achieving precise gain without requiring complex closed-loop control circuitry throughout the entire amplification process.
Solution Approach 2:
The amplifier operates periodically, alternating between the integration phase and regeneration phase controlled by non-overlapping clock signals. This periodic operation enables precise gain accumulation during integration while using simple regenerative feedback only during specific time intervals, reducing overall device complexity compared to continuous closed-loop operation.
2Measurement precision
If traditional closed-loop amplifiers are used to achieve precise gain, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The amplifier uses periodic operation with distinct integration and regeneration phases. During the integration phase, power consumption is minimized as charge accumulates on capacitors without active feedback. The regenerative phase consumes power only briefly to restore signal levels. This periodic action dramatically reduces average power consumption compared to continuous closed-loop amplification while maintaining precise gain through the integration process.
Solution Approach 2:
The continuous feedback loop is extracted and replaced with periodic regenerative feedback applied only during the regeneration phase. This removes the need for continuous power-consuming feedback operation while preserving the essential function of gain control through the integration phase, thereby reducing overall power consumption.
3Use of energy by moving object
If dynamic amplifiers are used to reduce power consumption, then power efficiency is improved, but measurement precision deteriorates
Solution Approach 1:
The dynamic amplifier is segmented into an integration phase for precise gain accumulation and a regeneration phase for signal restoration. The integration phase uses simple charge accumulation on capacitors without feedback, achieving precise gain with minimal power consumption. The regeneration phase briefly applies regenerative feedback to restore signal levels, correcting any precision degradation while consuming minimal average power.
Solution Approach 2:
The integration phase performs preliminary gain accumulation on capacitors before the regeneration phase restores signal levels. This preliminary action establishes the precise gain relationship early in the cycle, allowing the subsequent regeneration phase to work with already-amplified signals, thereby improving overall gain accuracy while maintaining power efficiency.
4Device complexity
If open-loop residue amplification is used to reduce amplifier gain requirements, then device complexity is reduced, but measurement precision deteriorates due to increased non-linearity
Solution Approach 1:
The amplification is segmented into integration and regeneration phases. During integration, charge accumulates linearly on capacitors without feedback, maintaining excellent linearity. During regeneration, brief regenerative feedback is applied to restore signal levels and correct non-linearities. This segmentation achieves simple open-loop operation while preserving linearity through the disciplined two-phase structure.
Solution Approach 2:
Periodic regenerative feedback is applied during the regeneration phase to correct non-linearities that would otherwise accumulate. This periodic correction, synchronized with the integration-regeneration cycle, maintains linearity without requiring continuous feedback, thereby preserving the benefits of open-loop operation while improving measurement precision.
5Use of energy by moving object
If integrator-based amplifiers are used to achieve high power efficiency, then power efficiency is improved, but measurement precision deteriorates due to limited maximum gain
Solution Approach 1:
The amplifier is segmented into an integration phase that can accumulate gain over an extended period and a regeneration phase that restores signal levels. The integration phase benefits from extended integration time to achieve high gain with high power efficiency, while the regeneration phase periodically restores signals to prevent saturation. This segmentation enables both high maximum gain and high power efficiency simultaneously.
Solution Approach 2:
The integration phase performs preliminary gain accumulation over an extended period before regeneration is needed. This preliminary action allows the amplifier to achieve high gain values through prolonged integration while consuming minimal power, with regeneration only periodically restoring signal levels to extend the dynamic range and maximum achievable gain.
Data Source
AI summary
A variable gain amplifier utilizing positive feedback and time-domain calibration includes an integration phase and a regeneration phase. A current source provides a bias current that increases linearity in the integration phase and reduces common-mode voltage dependence. The circuit includes a timing control loop, wherein a variable gain of a residue amplifier is proportional to a first time that a timing control loop signal is kept high, as determined by an on or off status of respectively paired inverter assemblies each having an input voltage determined by an amplifier output voltage during the regeneration phase. A strong-arm latch structure acts as a positive feedback latch until the first time is de-asserted.