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 distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
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 teacher head, 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".