Chopper-Stabilized PGA Current Mirror for Low-Noise ADC Input
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Solution Overview
Problem
Analog signals exceeding the voltage range of an analog-to-digital converter (ADC) require attenuation or amplification, but existing solutions do not effectively manage noise and current element mismatch, especially when operating between different voltage domains.
Innovation Solution
A programmable gain amplifier (PGA) with a current-to-voltage amplifier and a current mirror configuration, employing a 1:M current mirror ratio and chopping technique to reduce noise and eliminate mismatch effects, while adjusting the common mode voltage and providing adjustable gain for the ADC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a PGA is used to attenuate or amplify analog signals for ADC input, then the signal can be adjusted to fit the ADC voltage range, but noise and current element mismatch are not effectively managed
Solution Approach 1:
The patent implements chopping technique that periodically switches the current mirror configuration between different states (attenuation and amplification modes). This periodic switching allows the system to average out noise and mismatch effects over time, effectively reducing their impact on signal accuracy while maintaining the ability to adjust signal levels for ADC input.
Solution Approach 2:
The patent changes the operational parameters of the current mirror by dynamically adjusting the mirror ratio (1:M where M ≥ 1) and switching between different chopping phases. This parameter modulation enables the system to optimize noise performance and mismatch rejection at different operating points while maintaining programmable gain functionality.
2Adaptability or versatility
If existing PGA solutions are used to manage signals between different voltage domains, then signal level adjustment is achieved, but noise performance and mismatch effects are not adequately reduced
Solution Approach 1:
The patent introduces a current-to-voltage amplifier as an intermediary stage between the voltage domain interface and the ADC. This intermediary converts current signals from the voltage domain interface into voltage signals suitable for the ADC, while the chopping technique applied to the current mirror reduces noise and mismatch in the intermediate current signals, thereby improving overall reliability.
Solution Approach 2:
The chopping technique periodically switches the current mirror operation between different phases, allowing the system to reject noise and mismatch effects that are common in voltage domain interfaces. This periodic action maintains adaptability across different voltage domains while significantly improving noise performance and signal reliability.
Data Source
AI summary
A circuit including an amplifier having an input and an output. The circuit also includes a current-to-voltage amplifier having an input. The circuit further includes a current mirror coupled between the output of the amplifier and the input of the current-to-voltage amplifier. The current mirror is configured to chop current flowing through the first current mirror.