Residual Amplifier Common-Mode Compensation in Pipelined ADCs
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Solution Overview
Problem
In high-speed pipelined analog-to-digital converters, the common-mode value of the input signal of the residual amplifier is attenuated due to parasitic capacitance, leading to a deviation of the quiescent point from the reset value, which deteriorates the output swing, linearity, and overall performance of the converter.
Innovation Solution
An input common-mode compensation circuit is introduced, comprising an energy storage module, a switching selection module, and a feedback compensation module. During the reset stage, the energy storage module is charged using the reset voltage, and during the working stage, feedback compensation is applied to stabilize the common-mode value of the input signal near the reset voltage, thereby suppressing attenuation caused by parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If parasitic capacitance is present in the residual amplifier circuit, then the circuit can operate at high speed, but the common-mode value of the input signal is attenuated causing deviation from the reset value
Solution Approach 1:
The patent implements a feedback compensation circuit that monitors the common-mode value at the input of the residual amplifier and adjusts it through feedback control. The circuit uses operational amplifiers and resistors to detect the common-mode voltage deviation and generate a compensating signal that feeds back to restore the common-mode value to its intended level, thereby resolving the attenuation caused by parasitic capacitance while maintaining high-speed operation
Solution Approach 2:
The patent applies preliminary compensation by pre-adjusting the common-mode value before it is affected by parasitic capacitance attenuation. The compensation circuit proactively sets the common-mode voltage to a predetermined correct value at the input of the residual amplifier, counteracting the expected attenuation effect before it occurs during signal processing
2Speed
If the common-mode value deviates from the reset value, then high-speed operation is maintained, but the output swing and linearity deteriorate
Solution Approach 1:
The feedback compensation circuit continuously monitors the common-mode value and adjusts it in real-time to maintain accuracy. By using operational amplifiers configured in feedback topology with appropriate resistors, the circuit detects deviations from the reset value and generates corrective signals that restore the common-mode voltage, thereby preserving both high-speed operation and output linearity simultaneously
3Device complexity
If no compensation circuit is used, then the circuit structure remains simple, but the common-mode attenuation cannot be suppressed
Solution Approach 1:
The patent introduces a feedback compensation circuit that uses operational amplifiers and resistors to monitor and adjust the common-mode value. The feedback mechanism detects common-mode attenuation and generates corrective signals to restore the proper voltage level, providing reliable common-mode stability while maintaining relatively simple circuit implementation suitable for integrated circuits
Solution Approach 2:
The compensation circuit acts as an intermediary between the signal source and the residual amplifier. It introduces intermediate components (operational amplifiers and resistors) that mediate the common-mode voltage level, preventing direct attenuation by parasitic capacitance and ensuring stable common-mode operation without significantly complicating the overall circuit structure
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution effectively suppresses the input common-mode attenuation phenomenon of the residual amplifier in the working state, ensuring the stability of the common-mode value and maintaining the stable performance of the pipelined analog-to-digital converter without affecting the normal operation of the residual amplifier.
Implementation Method 1
the energy storage module includes a capacitor, one end of the capacitor is connected to the non-inverting input end of the residual amplifier
Implementation Method 2
the feedback compensation module includes a voltage amplifier, a first resistor, and a second resistor; an inverting input end of the voltage amplifier is connected to the non-inverting input end of the residual amplifier via the first resistor connected in series
Data Source
AI summary
An input common-mode compensation circuit includes an energy storage module, a switching selection module, and a feedback compensation module. An end of the energy storage module is connected to an input end of the residual amplifier. An input end of the switching selection module is connected to another end of the energy storage module. Input ends of the feedback compensation module are respectively connected to the end of the energy storage module and to a reset voltage of the residual amplifier, and an output end of the feedback compensation module is connected to an output end of the switching selection module. During the reset stage of a residual amplifier, the energy storage module is charged under the action of a reset voltage. During the working stage of the residual amplifier, feedback compensation is performed on the energy storage module through the feedback compensation module.