Highly Sensitive Amplifier Circuit Consisting of Complementary pFET-type and Resistor-type Gas Sensors

We propose a highly efficient amplifier circuit in which a resistor-type gas sensor is used as a complementary load to convert the sensing current of the FET-type gas sensor into a voltage. This circuit is designed so that two different sensors are connected in series and their currents change in opposite directions to increase the sensitivity in the gas response. To compare the performance of this amplifier, 4 different amplifier circuits are fabricated using only 6 masks and these are systematically analyzed. The amplifier circuit with complementary load at Vin in the range of 0.6 V to 0.66 V gives good linearity (R
²
> 0.98) and high sensitivity up to 8.96 mV/ppb to NO2 gas concentration changes, and has an excellent SNR of ~10
³
.