The Mathematical Model Of Frequency Gas Transducer Based On Transistor Structure With Ndr For Diagnosis Of Helicobacter Pylori Strains

The paper studies a frequency transducer of the gas concentration for detection of Helicobacter Pylori strains based on the MOSFET-bipolar transistor structure with a negative differential resistance and a highly sensitive NH3 sensor. A dynamic mathematical model of the frequency transducer of gas concentration has been developed using the state variable method which makes it possible to determinate the value of voltage or current at any point of the circuit at any particular time when the gas concentration is changed. Analytical expressions for transfer function and sensitivity equation have been obtained on the basis of the nonlinear equivalent circuit of the frequency gas concentration transducer. Sensitivity of the developed device for detecting Helicobacter Pylori strains is from 2.1 kHz/ppm to 3.4 kHz/ppm.