Dynamic Amplifier Common-Mode Control for Higher ADC Gain
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Solution Overview
Problem
Dynamic amplifiers in analog-to-digital converters (ADCs) face challenges in maintaining maximum achievable gain due to common-mode voltage shifts during amplification, which can lead to non-monotonic behavior and potential catastrophic failures.
Innovation Solution
Incorporating a current source that selectively applies a common-mode counter current to the differential outputs of the dynamic amplifier, either as a fixed or dynamic current source, to control and reduce common-mode voltage shifts, thereby extending amplification time and enhancing ADC performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the amplification time of the dynamic amplifier is extended to achieve maximum gain, then the achievable gain increases, but common-mode voltage shifts occur causing non-monotonic behavior and potential catastrophic failures
Solution Approach 1:
The patent applies preliminary anti-action by introducing a common-mode counter current before the harmful common-mode voltage shift can cause non-monotonic behavior. The counter current is generated in response to detecting a common-mode voltage change, and is applied to the differential outputs to preemptively counteract the harmful effect, allowing the amplifier to maintain stability during extended amplification periods.
Solution Approach 2:
The patent implements feedback by continuously monitoring the common-mode voltage at the differential outputs and using this information to control the generation and application of the common-mode counter current. When a common-mode voltage shift is detected, the feedback mechanism activates the counter current to correct the deviation, enabling the amplifier to maintain reliable operation throughout the extended amplification time.
2Manufacturing precision
If power supply voltage or transconductance is increased to achieve higher gain, then the maximum achievable gain increases, but power consumption and circuit complexity increase
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the common-mode counter current parameter in response to common-mode voltage shifts, rather than increasing the power supply voltage or transconductance. This allows the amplifier to achieve and maintain maximum gain throughout the extended amplification period while keeping power consumption constant, as the counter current is generated only when needed to counteract voltage shifts.
3Manufacturing precision
If power supply voltage or transconductance is increased to achieve higher gain, then the maximum achievable gain increases, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary element - the common-mode counter current - that mediates between the amplifier's amplification function and the common-mode voltage shifts. Rather than modifying the core amplifier structure (which would increase complexity), the counter current acts as an intermediary that corrects common-mode issues, allowing the amplifier to maintain high gain precision with minimal additional circuit complexity.
Data Source
AI summary
Techniques and apparatus for output common-mode control of dynamic amplifiers, as well as analog-to-digital converters (ADCs) and other circuits implemented with such dynamic amplifiers. One example amplifier circuit includes a dynamic amplifier and a current source. The dynamic amplifier generally includes differential inputs, differential outputs, transconductance elements coupled to the differential inputs, a first set of capacitive elements coupled to the differential outputs, and a control input for controlling a time length of amplification for the dynamic amplifier. The current source is configured to generate an output current such that portions of the output current are selectively applied to the differential outputs of the dynamic amplifier during at least a portion of the time length of amplification.