Chopper Amplifier Circuit With Feedback for Low-Noise Buffering
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Solution Overview
Problem
Conventional amplifier circuits using chopper modulation technology face challenges in achieving high input impedance and sufficient noise reduction, particularly when used as buffer circuits, due to asymmetry in circuit structure which lowers noise modulation performance.
Innovation Solution
The proposed amplifier circuit includes a first chopper circuit for differential signal amplification and a second amplifier circuit with a differential pair, current mirror, and negative feedback mechanism to convert differential signals to single-ended signals, reducing noise by maintaining symmetry and utilizing a feedback path to minimize voltage differences between nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional chopper modulation technology is used in amplifier circuits, then noise reduction is achieved, but input impedance cannot be sufficiently increased and circuit asymmetry degrades noise modulation performance
Solution Approach 1:
The patent intentionally introduces asymmetry through a dedicated current mirror circuit (second amplifier circuit) to convert the differential signal to single-ended output. This controlled asymmetry maintains the symmetry of the chopper modulation path while enabling proper signal conversion, thereby preserving noise modulation performance while achieving the desired output configuration.
Solution Approach 2:
The patent introduces a current mirror circuit as an intermediary component between the differential amplifier output and the final single-ended output. This intermediary circuit converts the differential signal to single-ended signal while maintaining the noise reduction benefits of the chopper modulation through proper circuit design.
2Object-affected harmful factors
If conventional amplifier circuit structures are used, then circuit simplicity is maintained, but noise reduction performance is insufficient
Solution Approach 1:
The patent divides the amplifier circuit into two distinct functional segments: a first amplifier circuit dedicated to chopper modulation and differential signal amplification, and a second amplifier circuit (current mirror) dedicated to signal conversion to single-ended output. This segmentation allows each segment to be optimized for its specific function, improving overall noise performance while maintaining clear functional separation.
Solution Approach 2:
The patent combines the chopper modulation function and the differential-to-single-ended conversion function into a single integrated amplifier circuit structure. The current mirror circuit is seamlessly integrated with the differential amplifier, allowing both functions to work together without requiring separate independent circuits, thus achieving noise reduction without excessive complexity.
3Object-affected harmful factors
If buffer circuit is implemented with conventional design, then high input impedance is achieved, but noise is not sufficiently reduced
Solution Approach 1:
The patent employs negative feedback through the current mirror circuit to stabilize the operating point and reduce noise. The feedback mechanism ensures that the buffer circuit maintains high input impedance while the chopper modulation actively reduces noise, achieving both goals simultaneously through coordinated circuit operation.
Data Source
AI summary
An amplifier circuit has: a first amplifier circuit, including a chopper circuit amplifying a first differential signal input between first and second input terminals to output a second differential signal; and a second amplifier circuit amplifying the second differential signal to output a single-ended signal. The second amplifier circuit includes: a first circuit including first and second transistors, the first circuit being connected to the first amplifier circuit so that the second differential signal input into gates of these transistors, the first circuit converting the second differential signal to a current flowing into a first node connected to the first transistor and a current flowing into a second node connected to the second transistor; and a second circuit negatively feeding back a voltage at the second node so that the difference in voltage between these nodes is reduced. The second amplifier circuit outputs the single-ended signal from the first node.