Switched-Resistor Amplifier Reset Sequencing for Bias Accuracy
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Solution Overview
Problem
Existing amplifier circuits with switched resistor units experience significant errors due to charge injection and parasitic capacitance, leading to prolonged settling times of input voltage bias and increased error influence when switches are turned on and off simultaneously.
Innovation Solution
The amplifier circuit design includes a first switched resistor unit connected to the input terminal and a second resistance element unit connected between the output terminal, with a control circuit exclusively controlling the switches to prevent overlapping on/off cycles, thereby minimizing the impact of charge injection errors and parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If switches are turned on and off simultaneously in the amplifier circuit, then the circuit operation is simplified, but charge injection errors and parasitic capacitance increase significantly
Solution Approach 1:
The patent applies preliminary action by resetting the common connection point to ground potential before switching operations. The second switch resets the node to ground before the first switch connects the resistance element, ensuring that charge injection and parasitic capacitance effects are minimized by establishing a known reference state beforehand.
2Loss of time
If the settling time for input voltage bias is reduced, then the circuit response speed improves, but the error influence from charge injection increases
Solution Approach 1:
The patent converts the harmful charge injection effect into a beneficial reset mechanism. By deliberately allowing charge injection to occur during the reset phase (when the second switch operates), the common connection point is brought to a known ground potential state, which actually improves measurement accuracy in the subsequent measurement phase.
3Speed
If multiple switches are operated simultaneously to achieve parallel resistance switching, then the switching speed improves, but the error superposition from charge injection worsens
Solution Approach 1:
The patent implements periodic action by sequentially operating switches in distinct phases rather than simultaneously. The control circuit alternates between reset phase (second switch active) and measurement phase (first switch active), creating a periodic switching pattern that prevents error superposition while maintaining effective switching speed through rapid phase alternation.
Data Source
AI summary
An amplifier circuit includes: an amplifier; a first switched resistor unit configured by connecting in series a first resistance element having one or more resistors and a first switch, and having one end connected to an input terminal of the amplifier; a second resistance element unit connected between an other end of the first switched resistor unit and an output terminal of the amplifier and including one or more resistors; a second switch connected between a common connection point of the first switched resistor unit and the second resistance element unit and a reset potential point; and a control circuit for exclusively turning on and off the first switch and the second switch, respectively.