Switched-Capacitor Sensor Amplifier for DC Current and Noise Control
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Solution Overview
Problem
Conventional amplifier arrangements for optoelectronic sensor frontends face challenges in efficiently processing sensor signals, particularly in eliminating unwanted DC currents and managing noise, while also requiring significant chip area and power consumption.
Innovation Solution
The proposed amplifier concept employs an integrating amplifier with a switched capacitor feedback loop, where the feedback path is connected to the forward path via a feedback capacitor in a switchable fashion, using an impedance element to regulate DC currents and reduce noise, allowing for both positive and negative current configurations without signal reference translation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional transimpedance amplifier with active DC feedback loop is used, then DC current regulation is achieved, but chip area and power consumption increase
Solution Approach 1:
The patent combines the integrating amplifier and DC feedback amplifier into a single unified circuit architecture. The feedback path of the integrating amplifier is directly connected to the output of the DC feedback amplifier, eliminating the need for separate DC feedback components and reducing chip area while maintaining DC current regulation capability
Solution Approach 2:
The DC feedback amplifier output is used dual-purpose: it provides DC current regulation and simultaneously serves as the feedback path for the integrating amplifier. This multi-functional design reduces the number of separate components needed, thereby reducing chip area and power consumption
2Productivity
If multiple amplifier stages are used for signal processing, then signal processing capability is improved, but device complexity increases
Solution Approach 1:
The patent merges the functions of the integrating amplifier and DC feedback amplifier into a single integrated stage. The direct connection of the feedback path eliminates the need for additional coupling components and reduces overall circuit complexity while maintaining enhanced signal processing capability
3Power
If conventional amplifier configurations are used, then signal amplification is achieved, but noise performance deteriorates
Solution Approach 1:
The patent employs a switched capacitor feedback mechanism in the integrating amplifier that provides active DC current compensation. This feedback approach reduces offset voltages and minimizes noise generation from DC current mismatches, improving overall noise performance while maintaining signal amplification
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
This solution results in a compact, low-noise, and high-linearity single-stage amplifier frontend suitable for photodiodes, capable of acting as a buffer for analog-to-digital converters, with reduced stability requirements and improved noise performance.
Implementation Method 1
An impedance element is coupled between the second amplifier output and the sensor input
Implementation Method 2
a switched integration capacitor that is charged by the feedback path during a first switching phase and discharged during a second switching phase
Implementation Method 3
in optoelectronics applications with photodiodes as receiver elements
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An amplifier arrangement comprises a sensor input (SI) for connecting a sensor, a first amplifier (OP1) and a second amplifier (OP2). The first amplifier (OP1) has a first amplifier output and a first and a second input, of which the first input is connected to a first reference potential terminal (VCM1), and of which the second input is connected to the sensor input (SI) in a direct fashion and to the first amplifier output via a first feedback path having a switched integration capacitor (CINT) that is charged by the feedback path during a first switching phase and discharged during a second switching phase. The second amplifier (OP2) has a second amplifier output and a first and a second input, of which the first input is connected to a second reference potential terminal (VCM2). A switched capacitor feedback has a first and a second feedback capacitor (CDC1, CDC2). The first feedback capacitor (CDC1) is connected in-between a first pair of feedback switches between the first amplifier output and the second reference potential terminal (VCM2) and in-between a second pair of feedback switches between the second reference potential terminal (VCM2) and the second input of the second amplifier (OP2). The second feedback capacitor (CDC2) is connected between the second amplifier output and the second input of the second amplifier (OP2). An impedance element (RDC) is coupled between the second amplifier output and the sensor input (SI).