Chopper Amplifier Bias Switching for Offset and Slew Rate
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Solution Overview
Problem
Existing amplifiers face challenges in eliminating offset voltages, which affect their performance and accuracy.
Innovation Solution
The amplifier employs routing circuits as choppers, coupled with a bias voltage generating circuit and compensation capacitors, to dynamically adjust bias voltages and exchange capacitors during switching periods, effectively offsetting offset voltages and maintaining gain linearity and improving slew rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If routing circuits are used as choppers to offset offset voltages, then offset voltage elimination is improved, but device complexity increases
Solution Approach 1:
The routing circuits are designed to perform multiple functions: they serve as signal routing switches and simultaneously function as choppers for offset voltage elimination. By making the routing circuits universal, the patent avoids adding separate dedicated chopping circuits, thus improving offset voltage elimination without proportionally increasing device complexity.
Solution Approach 2:
The patent combines the routing function and chopping function into a single circuit structure. The routing circuits are merged with the chopping operation by controlling them to swap input signals periodically, thereby eliminating offset voltages. This merging reduces the number of separate components and simplifies the overall circuit architecture.
2Stability of the object's composition
If bias voltages are dynamically adjusted during switching periods, then gain linearity is maintained, but control complexity increases
Solution Approach 1:
The bias voltage adjustment is performed periodically during switching periods, synchronized with the routing circuit switching. This periodic action maintains gain linearity by compensating for variations that occur during signal swapping, while the regular timing pattern simplifies the control mechanism compared to continuous adjustment.
Solution Approach 2:
The control mechanism uses feedback from the switching state to dynamically adjust bias voltages. The controller monitors the routing circuit switching and accordingly adjusts the bias voltages applied to the input stage circuit, creating a closed-loop system that maintains gain linearity through automated feedback control.
3Speed
If compensation capacitors are exchanged during switching, then slew rate is improved, but circuit complexity increases
Solution Approach 1:
The compensation capacitors are dynamically switched during operation rather than being fixed. The third routing circuit enables the capacitors to be exchanged between different circuit nodes during switching periods, allowing the system to adapt its compensation characteristics dynamically to improve slew rate while managing complexity through controlled switching.
Solution Approach 2:
The compensation capacitors are pre-charged or pre-positioned in specific configurations before the switching occurs. This preliminary action ensures that when the switching happens, the capacitors are already in the optimal state to provide immediate slew rate improvement, reducing the need for complex real-time adjustment mechanisms.
Data Source
AI summary
An amplifier including a first routing circuit, an input stage circuit, an output stage circuit, a second routing circuit, and a bias voltage generating circuit is provided. The bias voltage generating circuit generates a first bias voltage and a second bias voltage for respectively supplying a first tail current source and a second tail current source of the input stage circuit. During a first period, the first bias voltage is related to the voltage at a first input terminal of the amplifier, and the second bias voltage is related to the voltage at a second input terminal of the amplifier. During a second period, the first bias voltage is related to the voltage at the second input terminal of the amplifier, and the second bias voltage is related to the voltage at the first input terminal of the amplifier.