Operational Amplifier Offset Current Generator for Linearity
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Solution Overview
Problem
Existing A/D converters, operational amplifiers, and back electromotive force monitoring circuits face limitations in processing speed, circuit scale reduction, and linearity of offset adjustment, as well as accuracy in monitoring back electromotive force.
Innovation Solution
The proposed solutions include an A/D converter with a sequencer that performs input switching processing after sample hold, an operational amplifier with an offset current generator for precise offset adjustment, and a back electromotive force monitoring circuit that generates a speed detection voltage by biasing the back electromotive force with a reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the sequencer waits for completion of A/D conversion processing before performing input switching, then the conversion accuracy is ensured, but the processing speed decreases
Solution Approach 1:
The sequencer performs input switching processing in advance after sample hold completion, rather than waiting for the entire A/D conversion to finish. This preliminary action overlaps the switching preparation with the conversion process, reducing total processing time while maintaining accuracy through proper timing coordination.
2Manufacturing precision
If the operational amplifier uses a conventional offset adjustment method, then the circuit structure is simple, but the linearity of offset adjustment is poor
Solution Approach 1:
The patent changes the adjustment parameter from voltage-based to current-based offset adjustment. By using current sources that can be precisely controlled and summed, the linearity of offset adjustment is significantly improved while the circuit complexity remains manageable through systematic current mirror design.
3Measurement precision
If the back electromotive force monitoring circuit directly monitors the generated back electromotive force, then the circuit is simple, but the monitoring accuracy is insufficient
Solution Approach 1:
The patent introduces an operational amplifier as an intermediary device that conditions the back electromotive force signal before measurement. The op-amp amplifies and stabilizes the signal, providing a cleaner, more accurate input to the monitoring circuit while maintaining overall circuit simplicity through the use of a single high-performance component.
Data Source
AI summary
An operational amplifier has an input stage which generates a first input current and a second input current in accordance with a first input signal and a second input signal, an offset adjuster which gives offsets to the first input current and the second input current respectively to generate a first output current and a second output current, an output stage which generates an output signal in accordance with the first output current and the second output current, and an offset current generator which generates a first offset current and a second offset current in accordance with an offset adjustment signal. The offset adjuster gives the offsets to the first input current and the second input current respectively by using the first offset current and the second offset current.