Feedback Amplifier Circuit for High-Impedance Sensor Readout
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Solution Overview
Problem
Conventional amplifying devices for sensors with high sensitivity face limitations in increasing input impedance, leading to reduced power consumption and noise suppression, which affects the ability to read signals from sensors effectively.
Innovation Solution
The proposed amplifying device incorporates a main amplifier, a first feedback circuit, an input coupling circuit, and an amplifying feedback circuit with negative feedback loops, which includes additional chopping circuits to enhance input impedance by compensating for parasitic capacitance and leakage current, allowing for increased input impedance even at lower gains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If conventional amplifying device uses three or more operational amplifiers to increase input impedance, then input impedance is improved, but power consumption increases and noise suppression deteriorates
Solution Approach 1:
The patent changes the circuit configuration parameters by introducing a specific feedback network with capacitors C1 and C2 connected to the inverting input terminal, along with a chopping circuit that periodically switches the feedback path. This parameter change enables high input impedance through capacitive feedback rather than through multiple operational amplifiers, thereby reducing power consumption while maintaining noise suppression performance
2Reliability
If gain of the amplifying device is lowered to prevent saturation of output signal, then output signal saturation is avoided, but input impedance is lowered which affects signal reading capability
Solution Approach 1:
The patent implements a feedback mechanism where capacitors C1 and C2 form a feedback network connected to the inverting input terminal, and a chopping circuit periodically switches the feedback path. This feedback structure creates a virtual ground effect that maintains high input impedance independently of the amplifier gain setting, allowing the device to read high-impedance sensor signals effectively even when operating at lower gain levels to prevent output saturation
Data Source
AI summary
An amplifying device includes a main amplifier; a first feedback circuit coupled between an input terminal of the main amplifier and an output terminal of the main amplifier; an input coupling circuit coupled between the input terminal of the main amplifier and a first node; and an amplifying feedback circuit coupled between the output terminal of the main amplifier and the first node, wherein the first feedback circuit and the amplifying feedback circuit are negative feedback circuits.