HIGH-FREQUENCY AUTOGENERATOR MICROELECTRONIC GAS SENSORS

Abstract

Ultra-high-frequency autogenerator microelectronic gas sensors based on transistor structures with negative differential resistance with primary gas-sensitive elements based on an MOS capacitive structure and an MOS field-effect transistor with an isolated channel are proposed, and the primary gas-sensitive elements are active elements of sensor autogenerator circuits, which simplifies the design of devices .

Based on the consideration of physical processes in the primary gas-sensitive elements and autogenerators of sensors, mathematical models of gas transducers were developed, on the basis of which parametric dependences of conversion and sensitivity functions were obtained. It is shown that the main contribution to the conversion and sensitivity functions is made by the change in gas concentration. This causes a change in the equivalent capacitance and negative differential resistance of the autogenerators of the sensors, which, in turn, changes the output frequency of the devices. The sensitivity of gas sensors varies from 0.55 kHz/ppm to 1.63 kHz/ppm in the measured concentration range from 0 ppm to 2000 ppm.

The obtained parametric dependences of the conversion and sensitivity functions show the possibility of obtaining the main characteristics of the sensors much more easily and clearly demonstrate the influence of each parameter of the primary converters and autogenerator parameters on the output frequency of the sensors in comparison with the calculations of the conversion and sensitivity functions from the equivalent circuits of the devices based on the solution of the Kirchhoff equations.

Gas sensors with frequency output do not require analog-digital converters and amplifiers for further processing of information signals, which reduces the cost of information and measurement equipment, in addition, it is possible to transmit information over a distance when the sensors work in the ultra-high frequency range.