Improving the Signal to Noise Ratio of QTF Preamplifiers Dedicated for QEPAS Applications

Abstract

The signal-to-noise ratio (SNR) is a major factor that limits the detection sensitivity of quartz-enhanced photoacoustic spectroscopy (QEPAS) sensors. The higher the electrical signal level compared to the noise amplitude is the lower the concentration of gases that can be detected. For this reason the preamplifier circuits used in QEPAS should be optimized for low-frequency narrow-band applications. Moreover, special care should be taken when choosing a particular operational amplifier in either a transimpedance or voltage (differential) configuration. It turns out that depending on the preamp topology different operational amplifier parameters should be carefully considered when a high SNR of the whole QEPAS system is required. In this article we analyzed the influence of the crucial parameters of low-noise operational preamplifiers used in QEPAS applications and show the resulting limitations of transimpedance and voltage configurations.

Study of the effect of the low-pass filter time constant on the noise level of quartz-enhanced photoacoustic spectroscopy sensors

“…𝑉 𝑛,𝑟𝑚𝑠 (𝑓 𝑠 ) = √∫ 𝑆 𝑂𝑈𝑇,𝑇𝑂𝑇 (𝑓) • 𝑑𝑓 𝑓 𝑠 +𝐸𝑁𝐵 𝑓 𝑠 −𝐸𝑁𝐵 (11) It is worth noticing that ENB depends on both the filter time constant τ and the filter order n [29]:…”

“…This mechanic deflection is converted into an electrical signal, which must be conveniently amplified by suitable front-end electronics [5][6][7]. Among the different preamplifier architectures for the readout of the QTF signal [8][9][10][11], transimpedance amplifiers (TIAs) represent the-state-of-the-art [12][13][14][15][16]. TIAs convert the QTF current signal into a voltage output signal by means of a feedback resistor (~10 MΩ), which must be properly designed in order to achieve the best performance in terms of Signal to Noise Ratio (SNR).…”

Quartz-Enhanced Photoacoustic and Photothermal Spectroscopy

“…Two manuscripts were dedicated to the design, development and optimization of high-performance electronics devoted to the QTF piezo-current transduction in a voltage signal. Piotr Z. Wieczorek et al analyzed the influence of the crucial parameters of the lownoise operational preamplifier design, and discussed the characteristics of transimpedance and voltage configurations [13]. G. Menduni et al investigated the possibility of using a differential input/output configuration with respect to single-ended configuration, and discussed the related signal-to-noise ratios in QEPAS spectra obtained by means of a water vapor sensor [14].…”

Influence of the Gain–Bandwidth of the Front-End Amplifier on the Performance of a QEPAS Sensor

“…Although voltage-mode front-end preamplifiers for the QTF have been proposed in the literature [10][11][12][13], the most common circuit configuration for interfacing the QTF is still the classic transimpedance preamplifier (TIA), schematically represented in Figure 3 [14][15][16][17].…”