Title :
Liquid Crystal Sensor Microchip
Author :
Hassanzadeh, Alireza ; Lindquist, Robert G.
Author_Institution :
Electr. & Comput. Eng. Dept., Univ. of Alabama, Huntsville, AL, USA
fDate :
5/1/2012 12:00:00 AM
Abstract :
In this paper, integration of liquid crystal (LC) capacitive chemical and biological sensor with the CMOS interface circuit has been investigated. The LC microchip provides better sensitivity compared to discrete interfacing and array of sensors can be fabricated to reduce false positives. For high sensitivity detection, the excitation signal voltage and frequency have been examined and sensor capacitance plots are provided. Two on-chip interdigitated capacitors provide differential sensor measurement to cancel common environmental parasitic effects. The LC sensor interface circuit includes a low noise charge amplifier, synchronous demodulator, low pass filter and a sigma-delta A/D converter. The preamplifier noise has been minimized using a nonlinear optimization algorithm. The preamplifier has 15 aF resolution with 1 kHz bandwidth, while the microchip has 14-bit resolution using AMI 0.5 μm technology.
Keywords :
CMOS analogue integrated circuits; biosensors; capacitive sensors; chemical sensors; circuit optimisation; demodulators; integrated circuit noise; interdigital transducers; liquid crystal devices; low noise amplifiers; low-pass filters; nonlinear programming; preamplifiers; sensor arrays; sigma-delta modulation; AMI technology; CMOS interface circuit; LC sensor interface circuit; differential sensor measurement; environmental parasitic effect cancellation; excitation signal frequency; excitation signal voltage; high sensitivity detection; liquid crystal capacitive biological sensor; liquid crystal capacitive chemical sensor; liquid crystal sensor microchip; low noise charge amplifier; low pass filter; nonlinear optimization algorithm; on-chip interdigitated capacitors; preamplifier noise minimization; sensor arrays; sensor capacitance plots; sigma-delta A/D converter; size 0.5 mum; synchronous demodulator; 1f noise; Capacitance; Capacitors; Materials; Sensitivity; Transistors; Capacitive transduction; liquid crystal sensor; low noise folded cascode amplifier; system integration;
Journal_Title :
Sensors Journal, IEEE
DOI :
10.1109/JSEN.2011.2174219
