Analog Delay Line Gain Stabilization via Transconductance Feedback
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Solution Overview
Problem
Existing analog delay lines face challenges in maintaining a differential signal amplitude at a minimum to reduce power consumption and sensitivity to supply voltage variations, due to difficulties in controlling the gain of differential amplifiers amidst process, supply voltage, and temperature variations.
Innovation Solution
A compensating circuit is implemented to adjust the bias voltage applied to the current sink transistor, and a differential-to-single converter is used to adjust the transconductance of input transistors, ensuring the gain of differential amplifiers remains substantially unity, thereby maintaining a constant current draw and minimizing signal amplitude variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gain of differential amplifiers is increased to ensure signal propagation through the delay line, then the signal amplitude is maintained, but power consumption increases and sensitivity to supply voltage variations worsens
Solution Approach 1:
A feedback mechanism is implemented using a differential amplifier that monitors the actual gain of the delay line and adjusts the bias current of the differential amplifiers accordingly. This closed-loop control ensures the gain remains at a precise value, allowing the signal to propagate reliably while maintaining minimum amplitude and reducing power consumption.
Solution Approach 2:
The bias current of the differential amplifiers is dynamically adjusted based on process, supply voltage, and temperature variations. By changing the operating parameters of the amplifiers in real-time, the system maintains optimal gain and signal amplitude under varying conditions, preventing excessive power consumption while ensuring reliable signal propagation.
2Reliability
If the gain of differential amplifiers is increased to maintain signal amplitude, then signal propagation is ensured, but sensitivity to supply voltage variations increases
Solution Approach 1:
The feedback mechanism continuously monitors the gain of the delay line and adjusts the bias current to compensate for supply voltage variations. This closed-loop control reduces sensitivity to supply voltage changes by actively counteracting their effects, ensuring stable signal propagation without excessive amplitude variations.
Solution Approach 2:
The system preemptively adjusts the bias current of the differential amplifiers based on detected supply voltage variations or process conditions. By making compensatory adjustments before signal degradation occurs, the system cushions against the harmful effects of supply voltage variations and maintains stable signal propagation.
3Use of energy by moving object
If the amplitude of the differential signal is reduced to minimize power consumption, then power consumption decreases, but it becomes difficult to ensure adequate propagation through the delay stages
Solution Approach 1:
The feedback mechanism ensures that the gain of each delay stage is precisely controlled to provide just enough amplification for the signal to propagate through the delay line. This allows the input signal amplitude to be minimized for low power consumption while the feedback-controlled gain ensures adequate signal levels are maintained throughout the delay stages.
4Use of energy by moving object
If the gain of differential amplifiers is precisely controlled to unity, then signal amplitude is minimized and power consumption is reduced, but control becomes difficult amidst process, supply voltage, and temperature variations
Solution Approach 1:
Rather than attempting to precisely control each differential amplifier's gain through complex design, the invention uses a feedback mechanism that measures the actual gain and automatically adjusts the bias current to achieve the desired unity gain. This approach trades additional control circuitry for simplified individual amplifier design while achieving precise overall gain control.
Solution Approach 2:
The feedback control system automatically adjusts the bias current based on the actual performance of the delay line, making the system self-regulating. The circuit monitors its own gain and corrects deviations without external intervention, simplifying the design of individual amplifiers while maintaining precise overall gain control under varying conditions.
Data Source
AI summary
Embodiments of delay lines may include a plurality of delay stages coupled to each other in series from a first stage to a last stage. Each delay stage may include an input transistor receiving a signal being delayed by the delay line. The delay line may include a compensating circuit configured to compensate for a change in a transconductance of the input transistor resulting from various factors. One such compensating circuit may be configured to provide a bias signal at an output node having a magnitude that is a function of a transconductance of a transistor in the compensating circuit. The bias signal may be used by each of the delay stages to maintain the gain of the respective delay stage substantially constant, such as a gain of substantially unity, despite changes in a transconductance of the respective input transistor in each of the delay stages.