Switched-Capacitor Sensor Amplifier for DC Current Compensation
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Solution Overview
Problem
Conventional sensor frontend amplifier arrangements face challenges in efficiently processing sensor signals, particularly in optoelectronic applications, due to limitations in handling DC currents and noise, and require complex configurations that consume chip area and power.
Innovation Solution
The proposed amplifier concept employs an integrating amplifier in the forward path with a switched capacitor feedback loop, using an impedance element to regulate DC currents, allowing for both positive and negative current compensation without signal reference translation, and incorporating a switched capacitor single stage amplifier frontend with active DC feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional two-stage amplifier configuration is used with TIA and integrator, then the sensor signal can be processed, but the chip area and power consumption increase
Solution Approach 1:
The patent combines the TIA and integrator functions into a single switched-capacitor amplifier stage. The first amplifier performs transimpedance conversion while the second amplifier performs integration, both within one unified stage that shares common components and timing structures, thereby reducing the total chip area compared to two separate stages.
Solution Approach 2:
The switched-capacitor feedback network serves multiple functions simultaneously: it provides the transimpedance conversion gain, implements the integration function through capacitive charging/discharging during different phases, and enables DC feedback for offset compensation. This multi-functionality eliminates the need for separate dedicated circuits for each function.
2Measurement precision
If a conventional two-stage amplifier configuration is used with TIA and integrator, then the sensor signal can be processed, but the power consumption increases
Solution Approach 1:
The patent merges two amplifier stages into one unified switched-capacitor stage, which operates using clocked switching rather than continuous operation. This reduces the average power consumption while maintaining the signal processing functions of both TIA and integrator through time-multiplexed operation of shared components.
Solution Approach 2:
The amplifier uses periodic clocked switching to alternately perform transimpedance conversion and integration functions. The switched-capacitor feedback operates in discrete phases controlled by clock signals, replacing continuous analog operation with periodic digital-like switching, thereby reducing average power consumption while maintaining processing capability.
3Reliability
If switched capacitor feedback is used with integrating amplifier, then DC current regulation is achieved, but circuit complexity increases
Solution Approach 1:
The patent implements a switched-capacitor feedback path that samples the output voltage and feeds it back through capacitors and switches to regulate the DC current at the sensor input. The feedback operates in discrete phases, using capacitor charging/discharging to adjust the DC operating point, providing automatic regulation without requiring complex continuous control circuits.
Solution Approach 2:
The switched-capacitor network acts as an intermediary between the output and the input, using charge transfer through capacitors during switching phases to implement DC feedback. This intermediary approach allows DC regulation to be achieved through simple capacitive coupling and switching rather than requiring complex direct DC feedback paths.
4Adaptability or versatility
If impedance element is used for DC current regulation, then both positive and negative currents can be compensated, but noise may increase
Solution Approach 1:
The patent uses a switched-capacitor feedback mechanism that dynamically changes the effective feedback impedance based on the required current direction. By alternating the switching states and capacitor connections, the circuit can compensate for both positive and negative DC currents while keeping the physical impedance elements (resistors) at optimized values that minimize noise, rather than requiring high-value resistors that would increase thermal noise.
Data Source
AI summary
An amplifier arrangement comprises a sensor input and a first and a second amplifier. The first amplifier has a first amplifier output and a first input connected to a first reference potential terminal and a second input connected to the sensor input in a direct fashion and to the first amplifier output via a feedback path having a switched integration capacitor that is charged by the feedback path during a first switching phase and discharged during a second switching phase. The second amplifier has a second amplifier output, a first input connected to a second reference potential terminal and a second input. A first feedback capacitor is connected in-between two pairs of feedback switches. A second feedback capacitor is connected between the second amplifier output and the second input of the second amplifier. An impedance element is coupled between the second amplifier output and the sensor input.