Differential Amplifier Chopper Circuit for Low DC Offset
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Solution Overview
Problem
Differential amplification devices suffer from DC offset voltage issues, which degrade the signal-to-noise ratio, especially when handling minute signals, due to fluctuations in element characteristics and manufacturing factors.
Innovation Solution
A differential amplification device is designed with a chopper switch circuit, V-I conversion circuit, and capacitance circuit that switches the input signal between normal and reverse phases, effectively converting and canceling out DC offset voltage through clock signal-controlled operations, thereby reducing its impact on the output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a differential amplifier is used to amplify minute signals, then the amplification capability is improved, but DC offset voltage appears at the output due to element characteristic fluctuations
Solution Approach 1:
The patent applies periodic chopping action to the input signal using switching elements, converting the DC offset voltage into an AC signal that can be filtered out. The chopper circuit periodically switches the input signal between normal and reverse phases, transforming the DC component into an AC component at the chopping frequency, which is then eliminated by filtering.
Solution Approach 2:
The patent converts the harmful DC offset voltage into a beneficial form by transforming it into an AC signal through periodic chopping. This converted AC signal can then be easily filtered out using standard filtering techniques, turning the originally harmful DC offset into a removable AC component that improves overall signal quality.
2Power
If DC offset voltage is present at the output, then the amplification function is maintained, but the signal-to-noise ratio deteriorates when handling minute signals
Solution Approach 1:
The patent extracts and separates the DC offset voltage from the useful signal by applying periodic chopping. The DC component is converted into an AC component at a specific frequency, allowing it to be selectively removed through filtering while preserving the original signal, thus extracting the harmful DC offset from the signal path.
Solution Approach 2:
The chopper circuit acts as an intermediary that transforms the DC offset voltage into an AC signal. This intermediate transformation allows standard filtering techniques to be applied, creating a mediator stage that converts the problematic DC component into a form that can be easily eliminated without affecting the useful signal.
3Ease of manufacture
If element characteristics fluctuate due to manufacturing factors, then the device can be manufactured with standard processes, but DC offset voltage is generated
Solution Approach 1:
The patent implements a self-correcting mechanism where the circuit automatically compensates for DC offset voltage generated by manufacturing variations. The chopper circuit and filtering mechanism work together to automatically eliminate the DC offset component without requiring external calibration or adjustment, allowing the device to self-correct for manufacturing tolerances.
Data Source
AI summary
Provided is a differential amplification device reduced in DC offset voltage. The amplification device amplifies an input signal, and includes a chopper switch circuit which switches the polarity of the input signal between a normal phase and a reverse phase and outputs the input signal, a V-I conversion circuit which is connected to the chopper switch circuit, a capacitance circuit which is connected to the V-I conversion circuit to store electric charges supplied from the V-I conversion circuit, and an amplification circuit which is connected to the V-I conversion circuit to switch the polarity of an input signal between the normal phase and the reverse phase and amplify the input signal.