Auto-Zeroed Amplifier Leakage Control for Longer Hold Time
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Solution Overview
Problem
Auto-zeroed amplifiers suffer from significant leakage current during the hold phase due to large voltage differences across switches, limiting the operational time between auto-zeroing periods.
Innovation Solution
The introduction of a leakage control circuit with switches that are enabled and disabled in inverse phases to limit the voltage across the capacitor, reducing the leakage current by ensuring the voltage across the switch is only a few milli- or micro-volts during the hold phase, thereby extending the operational time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional auto-zeroed amplifier is used, then amplifier offset is compensated, but leakage current through the switch is large due to large voltage difference, limiting operational time
Solution Approach 1:
The patent applies dynamics by making the switch configuration dynamic - switches are enabled and disabled in inverse phases during different operation phases (auto-zero phase vs. hold phase). This dynamic switching allows the circuit to adapt its characteristics: during the hold phase, the leakage control switches limit the voltage across the capacitor to only a few milli- or micro-volts, reducing leakage current from tens of microseconds hold time to tens of milliseconds hold time
Solution Approach 2:
The patent changes the voltage parameter across the capacitor dynamically. During the hold phase, instead of maintaining the full output voltage across the capacitor (which causes large leakage), the leakage control circuit limits the voltage across the capacitor to only a few milli- or micro-volts. This parameter change directly reduces the leakage current through the switch, extending the operational hold time between auto-zeroing periods
2Ease of operation
If the voltage across the switch is large during hold phase, then the amplifier can operate, but leakage current increases significantly
Solution Approach 1:
The patent uses periodic action by implementing periodic auto-zeroing phases alternating with extended hold phases. During the hold phase, leakage control switches are enabled to limit voltage and reduce leakage current. The system periodically returns to auto-zero phase to recalibrate, creating a rhythm of operation that minimizes energy loss during the extended hold periods while maintaining amplifier functionality
Solution Approach 2:
The patent introduces leakage control switches as intermediary elements between the main amplifier circuit and the capacitor. These intermediary switches specifically control the voltage across the capacitor during the hold phase, limiting it to a few milli- or micro-volts. This intermediary mechanism allows the amplifier to remain operational while significantly reducing the leakage current that would otherwise flow through the main signal path
Data Source
AI summary
An amplifier having an inverting input and a non-inverting input; a capacitor coupled to inverting input of the amplifier; an input voltage conveyance control circuit, having a first switch and a second switch, the first switch coupled to the capacitor, and the second switch coupled to the non-inverting input of the amplifier; a reference voltage conveyance control circuit having a third switch and a fourth switch, a shared node coupled between third switch and fourth switch, the fourth switch coupled to the non-inverting input of the amplifier; a fifth switch coupled to an output of the amplifier; a leakage control circuit having a sixth switch and seventh switch, the sixth switch coupled between the inverting amplifier input and the fifth switch, the seventh switch coupled to the sixth switch and the capacitor; and a first resistor coupled from the output of the amplifier to the first switch.