Then a peak detector circuit extracts the largest signal response for the use of further signal processing. The peak detector will output the largest value from its input. No matter how the input changes, it holds the output at the highest level ever appears. To obtain this signal voltage, a high pass filter is realized by using a transconductance amplifier with the baseline voltage at the inverting input while feeding the output voltage from the peak detector to the noninverting input. The transconductance amplifier outputs a current proportional to the differences between its non-inverting input and inverting input.
Previous chips show that adaptive circuit is working when adapting to the baseline.
But problems are discovered that the leakage current through the switch severely degrades the performance when the circuit works after adaption. A chip including transconductance amplifier have been tested and showed satisfactory result. A chip including peak detector just came back and will be experimented in the very near future. Signal Processing Stage. Depending on how many sensors there are to determine the odor signature, the number of the adaptive circuitry is needed.