High-precision, resistor less gas pressure sensor and instrumentation amplifier in CNT technology

In this paper, a new high-precision, pressure sensor for sensing gas molecules using a controllable voltage-mode instrumentation amplifier (VMIA) in carbon nanotube field-effect transistor (CNTFET) technology is designed. The sensing mechanism is based on the applied force by Oxygen atoms on the surface of the carbon nanotube (CNT), which is considered as a movable electrode of sensing capacitor. The sensing mechanism is simulated in ANSYS which justifies the variations of sensing capacitance, while the sensor's output voltage is applied to an accurate instrumentation amplifier (IA) via a switched-capacitor sensor driver. Therefore, due to the controllability of the transconductance and gain parameters of a CNTFET, the IA circuit provides a constant and controllable differential gain of up to 52 dB in a flat −3dB bandwidth of up to 3.6 MHz, which provides a tunable common-mode rejection ratio (CMRR) of up to 121 dB in a 1.8 GHz flat, −3dB frequency bandwidth. Moreover, due to the use of the differential pair stage, the total harmonic distortion (THD) value is obtained less than 0.67%. Finally, the proposed IA circuit consumes only 45.1 µW with a 22.52 nV/√Hz equivalent input referred noise value at ±0.5 V supply.