Switched-Capacitor Reference Voltage Circuit for Offset Correction
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Solution Overview
Problem
Conventional reference voltage generators, particularly those using operational amplifiers, suffer from input offset voltage issues that lead to inaccuracies in the generated reference voltage, affecting overall circuit performance.
Innovation Solution
A reference voltage generator that includes a capacitor network and a switch control circuit to manage the connectivity of capacitors within the amplifier's feedback path, switching between modes to correct input offset voltage and produce a substantially constant reference voltage, utilizing a semiconductor device and current drivers to maintain accuracy across temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an operational amplifier is used in a conventional reference voltage generator, then the circuit can generate a reference voltage, but the input offset voltage causes inaccuracies in the generated reference voltage
Solution Approach 1:
The patent applies preliminary action by performing offset voltage correction before the reference voltage generation process. The capacitor is pre-charged to compensate for the input offset voltage in a first operational mode, and then the charged capacitor is inserted into the feedback path in a second operational mode to cancel out the offset voltage effect, thereby improving reference voltage accuracy
Solution Approach 2:
The patent implements periodic action through alternating between two operational modes. The circuit switches between a first mode (where the capacitor is charged to compensate for offset voltage) and a second mode (where the charged capacitor is inserted into the feedback path to correct the offset). This periodic switching eliminates the harmful input offset voltage effect while maintaining reference voltage generation
2Measurement precision
If a capacitor is inserted into the feedback path to correct input offset voltage, then reference voltage accuracy improves, but the circuit complexity increases due to additional switching control
Solution Approach 1:
The patent applies universality by designing the capacitor to serve multiple functions. The same capacitor is used both for charging to compensate for offset voltage in the first operational mode and for insertion into the feedback path to correct the offset in the second operational mode. This multi-functional approach reduces the need for additional components and simplifies the overall circuit complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces inaccuracies in the reference voltage generation by conserving charge and correcting input offset voltage, resulting in a stable reference voltage output that is constant over a range of temperatures, with the ability to adjust the voltage magnitude as needed.
Implementation Method 1
Conservation of charge in the capacitor network that occurs when switching between the first mode and the second mode provides a way to reduce inaccuracies of producing the reference voltage otherwise caused by the input offset voltage
Data Source
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AI summary
A reference voltage generator comprises: an amplifier; a capacitor network including one or more capacitors; and a switch control circuit to control connectivity of the capacitor network with respect to the input/output nodes of the amplifier. During operation, the switch control circuit controls connectivity of a first capacitor (in the capacitor network) in and out of a feedback path of the amplifier to produce a substantially constant reference voltage. For example, the reference voltage generator provides input offset voltage correction of the amplifier via repeatedly switching between: i) a first mode in which the first capacitor is absent from the feedback path of the amplifier during charging of the first capacitor, and ii) a second mode of inserting the charged first capacitor into the feedback path of the amplifier. Correction of the input offset voltage of the amplifier results in generation of a more accurate reference voltage over temperature.