Auto-Zero Amplifier Circuit With Continuous Null Output Capacitor
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Solution Overview
Problem
Conventional auto-zero amplifiers experience characteristic degradation and noise generation due to voltage fluctuations when switching between operation modes, particularly when used in high-precision circuits handling minute signals, as a result of leakage currents affecting capacitive charge shifts and incorrect offset correction.
Innovation Solution
Incorporating a third capacitor continuously connected to the output terminal of the null amplifier without a switch, ensuring stable operation by maintaining the load connection and reducing voltage fluctuations between auto-zero and amplifier phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If switching operation between auto-zero phase and amplifier phase is implemented to refresh capacitor charges, then offset correction accuracy is improved, but noise generation and characteristic degradation occur due to voltage fluctuations during switching
Solution Approach 1:
The capacitor is pre-connected to the output terminal of the null amplifier before mode switching occurs. This preliminary connection ensures that the load is already in place during the auto-zero phase, allowing charge refresh to proceed without causing voltage fluctuations or noise when transitioning to the amplifier phase.
Solution Approach 2:
By maintaining a continuous capacitive load on the null amplifier output through the pre-connected capacitor, the circuit provides beforehand cushioning against the harmful voltage fluctuations that would otherwise occur during mode switching. The capacitor acts as a buffer that stabilizes the output voltage regardless of the operational phase.
2Reliability
If switching operation is performed at certain time intervals to update capacitor charges, then reliability of offset correction is improved, but characteristic degradation occurs due to leakage current affecting charge stability
Solution Approach 1:
The capacitor remains continuously connected to the null amplifier output throughout both auto-zero and amplifier phases, providing an uninterrupted useful action. This continuous connection ensures that the capacitive load is always present to stabilize the output voltage, while still allowing periodic charge refresh during the auto-zero phase to maintain reliability.
Solution Approach 2:
The pre-connected capacitor serves as an intermediary element between the null amplifier output and the rest of the circuit. It mediates the interaction between the two operational phases by providing a stable capacitive load that prevents direct conflict between charge refresh operations and voltage stabilization requirements.
3Measurement precision
If the null amplifier operates as an ideal amplifier for offset correction, then measurement precision is improved, but the amplifier does not actually operate as an ideal amplifier due to real-world limitations
Solution Approach 1:
The circuit changes the operational parameters of the null amplifier by maintaining a continuous capacitive load connection. This parameter change allows the amplifier to operate in a mode where it can achieve ideal-like performance for offset correction purposes while the continuous connection ensures stable actual operation in real-world conditions.
Data Source
AI summary
According to one embodiment, an amplifier circuit is an auto-zero amplifier including a main amplifier, a null amplifier, and a capacitor connected to an output terminal of the null amplifier without interposing a switch for switching an operation mode provided at the output terminal.