Design of a Low-Voltage Charge-Sensitive Preamplifier Interfaced with Piezoelectric Tactile Sensor for Tumour Detection

Charge sensitive preamplifiers are indispensable components of transducer-interfacing systems as they are responsible for amplifying the signals detected by the sensor. The rapid scaling of MOSFETs in the modern era has made it quite difficult to design a charge-sensitive preamplifier that has high effective resistance, consumes low power, generates very little noise, and can operate at low frequencies. This work will target to design a charge sensitive preamplifier at a supply voltage of 1.1 V using the 65 nm technology node that is supposed to operate at low levels of frequency in the range of 10–100 Hz with a high gain and high net resistance. The proposed design was found to produce a maximum gain of 235 dB and a maximum effective resistance of 270 GΩ and having a very low value of noise spectral density (<0.7 mV/√Hz). The power consumed by the proposed design was also in the range of nW. The working of the amplifier is illustrated in a practical scenario by interfacing it with a tactile sensor which would be used in detection of submucosal tumours by adjudging their stiffness. The sensor is designed as a layered shell with piezoelectric material sandwiched between two layers of electric conductors. The modelled sensor is then interpreted in terms of a current source with a resistance and capacitance in parallel to interface it with the designed charge sensitive preamplifier. The output of the sensor is difference in potential in the range of a few mV which is proportional to the pressure acting upon it. The mentioned sensor is simulated in COMSOL, and the charge amplifier is designed in Cadence.