Coupling p+n Field-Effect Transistor Circuits for Low Concentration Methane Gas Detection

Xinyuan Zhou,Liping Yang,Xiang Ma,Ning Han,Yuzhi Bian,Yunfa Chen

doi:10.3390/s18030787

Abstract

Nowadays, the detection of low concentration combustible methane gas has attracted great concern. In this paper, a coupling p+n field effect transistor (FET) amplification circuit is designed to detect methane gas. By optimizing the load resistance (RL), the response to methane of the commercial MP-4 sensor can be magnified ~15 times using this coupling circuit. At the same time, it decreases the limit of detection (LOD) from several hundred ppm to ~10 ppm methane, with the apparent response of 7.0 ± 0.2 and voltage signal of 1.1 ± 0.1 V. This is promising for the detection of trace concentrations of methane gas to avoid an accidental explosion because its lower explosion limit (LEL) is ~5%. The mechanism of this coupling circuit is that the n-type FET firstly generates an output voltage (VOUT) amplification process caused by the gate voltage-induced resistance change of the FET. Then, the p-type FET continues to amplify the signal based on the previous VOUT amplification process.

Highlights

Methane is a highly flammable and explosive gas widely used in domestic and industrial applications
It is noteworthy that every magnification factor (MF) of the field effect transistor (FET) circuit with 2.0 kΩ is larger than that of the FET circuit with
The commercial sensor (MP-4) used in this coupling circuit has shown a response of 7.0 ± 0.2 to 10 ppm methane

Summary

Introduction

Methane is a highly flammable and explosive gas widely used in domestic and industrial applications. The trace concentration of methane should be detected fast and reliably in the environment to prevent dangerous explosions. Various methane sensors have been developed on the basis of catalytic combustion [5,6,7], metal oxide semiconductor (MOX) [8,9], infrared spectrum [10,11], gas chromatography [12,13], and optical fiber [14,15]. Su et al reported that the catalytic combustion MEMS (microelectro-mechanical systems) sensors can detect 4000 ppm methane [5]. Shaalan et al prepared the Co3 O4 nanoparticles with response (Ra/Rg) of ~1.03 to 2500 ppm methane [8]. There are still challenges in detecting the trace concentration methane. Therein, the MOX gas sensor enjoys a tremendous advantage due to a fast response, chemical stability and low cost [16,17,18]

Methods

Results

Conclusion