CMOS Multi-Frequency Lock-in Sensor for Impedance Spectroscopy in Microbiology Applications
Bibliographic record
Abstract
This paper presents the design of a CMOS lock-in amplifier (LIA) encapsulated with an impedance sensor for microbial monitoring applications. The custom integrated LIA is designed and fabricated in a 0.18-µm CMOS technology. It includes a fully differential switched-capacitor transimpedance amplifier as the main building block of the lock-in amplifier. In this design, chopper stabilization is used in the capacitive transimpedance amplifier to reduce the noise and improve the sensor's sensitivity. The proposed LIA contains a band-pass filter with 0.88 quality factor to pass signals at selectable center frequencies of 1, 2, 4, and 10 kHz; a programmable gain amplifier, a mixer, and a low-pass filter to extract impedance changes caused by microorganism growth at different frequencies. The transimpedance amplifier has a gain of 54.86 dB, and an input-referred noise of 58 pA/√Hz at 1 kHz. The whole sensor has a sensitivity of 240 mV/nA. It consumes a power of 817.56 µW from a 1.8V power supply and has a total harmonic distortion of -72.7 dB.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".