A High Precision Readout Circuit for Dielectric  Gas Sensors


Aim of the project

The design, fabrication and test of a very low noise and stable CMOS integrated circuit for the read-out of a MEMS capacitive gas sensor. The system aims for the low-cost detection of changes in combustible gas mixtures.


Project description

First prototypes of a new type of MEMS gas sensor, as shown in figure 1, have been developed in our laboratory.

MEMS-DGS permittivity
Figure 1: Micro-photo of the first prototype of the MEMS dielectric gas sensor. Figure 2: Calculated relative change in permittivity of some typical components in combustible gases.

The sensor measures the permittivity of the gas in the gaps between the fingers of a MEMS structure.  The relative changes in the dielectric constant for various gases are very small, typically in the ppm range. Accurate detection of these very small changes in capacitance requires very low noise and highly stable readout circuits.


Main challenges:

  • An ultra-low noise read-out amplifier needs to be designed in a commercially available CMOS process.
  • The operating frequency for optimal performance of both the sensor and the readout circuit should be investigated.
  • The sensor and electronics will be part of a multi-sensor system for measuring gas quality in home gas appliances and therefore needs to be low cost.

We offer an innovative project for a motivated MSc student interested in circuit design and sensor interfacing.

The project contributes to the “Sensors for New Gas” program of the Dutch Ministry of Economic Affairs, stimulating an increasing use of gas from sustainable resources in the future.



Ger de Graaf