Pipelined ADC Op-Amp Sharing With Switchable Feedback Capacitors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional pipelined analog-to-digital converters are limited by the response speed of operational amplifiers, particularly due to the time required for charging or discharging feedback capacitors, which restricts the overall performance and operating speed.
Innovation Solution
The implementation of a pipelined analog-to-digital converter with multiple candidate capacitors and a capacitor selection circuit that dynamically switches coupling relationships based on input signal magnitude, allowing only part of the capacitors to participate in signal generation, and charging them in groups to reduce charging and discharging times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional operational amplifiers with fixed feedback capacitors are used, then the circuit structure is simple, but the response speed is limited due to the time required for charging or discharging the feedback capacitors
Solution Approach 1:
The feedback capacitor is divided into multiple candidate capacitors (first candidate capacitor, second candidate capacitor, third candidate capacitor) with different capacitance values. These segmented capacitors can be selectively connected to the operational amplifier through switching circuits, allowing the system to choose appropriate capacitance values based on signal requirements, thereby reducing charging/discharging time and improving response speed.
Solution Approach 2:
The circuit transitions from a static fixed capacitor configuration to a dynamic reconfigurable capacitor network. Switching circuits enable real-time selection and reconfiguration of candidate capacitors based on input signal characteristics, allowing the feedback capacitance to adapt dynamically to different operating conditions and optimize response speed for various signal frequencies and amplitudes.
2Loss of time
If multiple candidate capacitors are introduced to improve response speed, then the charging and discharging time is reduced, but the circuit area increases
Solution Approach 1:
Multiple candidate capacitors are merged into a single reconfigurable feedback path. Instead of requiring separate feedback paths for different capacitance values, the invention combines all candidate capacitors into one shared feedback network with switching elements that selectively connect appropriate capacitors, thereby reducing overall circuit area while maintaining the ability to quickly switch between different capacitance values.
Solution Approach 2:
The switching circuits serve multiple functions: they select candidate capacitors based on signal characteristics, enable rapid switching between different capacitance values, and maintain circuit stability during transitions. This multi-functionality reduces the need for additional dedicated components, thereby minimizing circuit area expansion despite the introduction of multiple capacitors.
3Area of stationary object
If a single operational amplifier is shared by different circuit stages, then the circuit area is reduced, but the response speed may be affected by the sharing arrangement
Solution Approach 1:
The operational amplifier's feedback characteristics are dynamically changed by switching between different candidate capacitors based on the specific circuit stage requirements and signal characteristics. This parameter adjustment allows the shared operational amplifier to optimize its response speed for each particular application, maintaining high performance across different stages despite the sharing arrangement.
Solution Approach 2:
The switching circuits are configured to pre-select and connect the appropriate candidate capacitor before the operational amplifier needs to process the signal. This preliminary action ensures that the correct capacitance value is already in place when the signal arrives, eliminating any potential response delay that might occur during capacitor switching and maintaining high response speed in the shared configuration.
Data Source
AI summary
A pipelined analog-to-digital converter includes: a first switched capacitor network, a first digital-to-analog converter, a second switched capacitor network, a second digital-to-analog converter, and an operational amplifier. The outputs from the first switched capacitor network and the first digital-to-analog converter form a first subtraction signal. The outputs from the second switched capacitor network and the second digital-to-analog converter form a second subtraction signal. The operational amplifier is arranged to operably generate an output signal based on the first subtraction signal or the second subtraction signal, and to operably switch coupling relationship of multiple candidate capacitors of the operational amplifier based on the magnitude of an input signal of a prior stage circuit, so that only a portion of the multiple candidate capacitors could be participated in the generation of the output signal at a time.