Self-Regulated Bias Circuits for Efficient Adjustment of the Operating Temperature of Chemoresistive Gas Sensors

A bias circuit is required for chemoresistive gas sensors to appropriately adjust their operating temperature and facilitate the readout of their output response. If the sensor is properly biased, its overall performance regarding sensitivity, selectivity, and power consumption can be greatly enhanced. We have introduced the concept of self-regulated biasing as an alternative to the conventional fixed biasing methods. In self-regulated bias circuits, the gas sensor is an active component in its own bias circuit, so the operating point is dynamically adjusted during a measurement. This will provide the sensor with different modes of operation. Here, we have proposed two self-regulated bias circuits the operation of which is analytically and experimentally studied. Results show that the first circuit puts the sensor in a low-power idle mode when no target gas is presented, and hence the power consumption is considerably reduced and the sensor lifetime may be prolonged. The second circuit puts the sensor in a power-down mode upon sensing a gas. This state is held until the circuit is reset. So the second bias circuit acts as a gas latch besides other important features like increased safety in explosive environments. Obviously, other self-regulated bias circuits can be designed for additional desired modes of operations.