CMCP with Adaptive CM Cancelling
Stable and Simple
Circuit Structure and Operation
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CM signal suppression loop operation
- Adaptive CM cancelling loop added for TCMRR improvement
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Using LMS algorithm and differential displacement current control, CM-to-DM conversion minimized even in the presence of circuit and electrode mismatches
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Block Diagram
Pros
No stability issue caused by the variation of electrode impedances
No additional electrode for VDRL application or VCM sensing required
- VIN,CM itself suppressed
Input CM range (or input swing) requirement relaxed
Input CM range extended beyond supply rails
CMRR significantly improved even in the presence of circuit and electrode mismatches
Cons
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Significant power overhead caused by the CMCP
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Input-referred noise of the front-end LNA increased due to the contribution from CMCP
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Suffers from a trade-off between the input CM range improvement and input-referred noise degradation
- Linearity of the recording circuit degraded due to the intermodulation between the CM and DM signals
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Can be mitigated at the cost of higher power consumption
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