Low-voltage wideband compact CMOS variable gain amplifier

A novel low-voltage wideband CMOS variable gain amplifier (VGA) is proposed. Using a 0.13 /spl mu/m CMOS technology, the VGA exhibits a linear-dB controllable gain range of 40 dB with a bandwidth in excess of 130 MHz, while drawing only 50 /spl mu/A from a single 1 V power supply voltage.     

Comparative investigation of thermoelectric power and cooling modules

Experimental Techniques -     

Ultra‐Low‐Power Differential ISFET/REFET Readout Circuit

A novel ultra‐low‐power readout circuit for a pH‐sensitive ion‐sensitive field‐effect transistor (ISFET) is proposed. It uses an ISFET/reference FET (REFET) differential pair operating in weak‐inversion and a simple current‐mode metal‐oxide semiconductor FET (MOSFET) translinear circuit. Simulation results verify that the circuit operates with excellent common‐mode rejection ability and good linearity for a single pH range from 4 to 10, while only 4 nA is drawn from a single 1 V supply voltage.     

Temperature programmed desorption of F-doped SnO<Subscript>2</Subscript> films deposited by inverted pyrosol technique

Fluorine-doped tin dioxide (FTO) films were deposited on silicon wafers by inverted pyrosol technique using solutions with different doping concentration (F/Sn=0.00, 0.12, 0.75 and 2.50). The physical and electrical properties of the deposited films were analyzed by SEM, XRF, resistivity measurement by four-point-probe method and Hall coefficient measurement by van der Pauw method. The electrical properties showed that the FTO film deposited using the solution with F/Sn=0.75 gave a lowest resistivity of 3.2·10^–4 ohm cm. The FTO films were analyzed by temperature programmed desorption (TPD). Evolved gases from the heated specimens were detected using a quadruple mass analyzer for mass fragments m/z, 1(H⁺), 2(H₂ ⁺), 12(C⁺), 14(N⁺), 15(CH₃ ⁺), 16(O⁺), 17(OH⁺ or NH₃ ⁺), 18(H₂O⁺ or NH₄ ⁺), 19(F⁺), 20(HF⁺), 28(CO⁺ or N₂ ⁺), 32(O₂ ⁺), 37(NH₄F⁺), 44(CO₂ ⁺), 120(Sn⁺), 136(SnO⁺) and 152(SnO₂ ⁺). The majority of evolved gases from all FTO films were water vapor, carbon monoxide and carbon dioxide. Fluorine (m/z 19) was detected only in doped films and its intensity was very strong for highly-doped films at temperature above 400°C.     

Low‐Voltage Current‐Sensing CMOS Interface Circuit for Piezo‐Resistive Pressure Sensor

A new low‐voltage CMOS interface circuit with digital output for piezo‐resistive transducer is proposed. An input current sensing configuration is used to detect change in piezo‐resistance due to applied pressure and to allow low‐voltage circuit operation. A simple 1‐bit first‐order delta‐sigma modulator is used to produce an output digital bitstream. The proposed interface circuit is realized in a 0.35 µm CMOS technology and draws less than 200 µA from a single 1.5 V power supply voltage. Simulation results show that the circuit can achieve an equivalent output resolution of 9.67 bits with less than 0.23% non‐linearity error.     

State-space synthesis of oscillators based on the MOSFET square law

A state-space synthesis of oscillators based on the large-signal square-law characteristic of a MOSFET in saturation is presented. The approach is an extension of the recently proposed MOSFET square-law filter synthesis methodology. Simulation results demonstrate that oscillation at megahertz frequencies is attainable. The oscillation frequency is also electronically tunable. The total harmonic distortion (THD) is simulated as 0.1-3% for output voltages between 80 mV and 1.1 V peak-to-peak, respectively. This oscillation amplitude can be controlled by an additional CMOS limiter     

Synthesis of CdIn2Se4 and Cu0.5Ag1.5InSe3 Compounds via Chemical and Solid-State Methods

CdIn₂Se₄ and Cu_0.5Ag_1.5InSe₃ are high-performance thermoelectric materials. In this study, both CdIn₂Se₄ and Cu_0.5Ag_1.5InSe₃ powders were synthesized using a microwave and solution method followed by annealing in nitrogen atmosphere. CdIn₂Se₄ was synthesized by two routes. First, CdSe was prepared using a microwave method. Second, In metal was prepared using a solution method. The prepared metals were annealed in nitrogen atmosphere. From the x-ray diffraction (XRD) results, CdIn₂Se₄ was observed as the main phase with CdSe and In₂O₃ as contaminant phases. The synthesis of Cu_0.5Ag_1.5InSe₃ was also divided into two steps. First, CuAg and Se were prepared using a microwave method. Second, In metal was prepared using a solution method. The prepared metals were annealed in nitrogen atmosphere. From the XRD results, Cu_0.5Ag_1.5InSe₃ was observed as the main phase with Cu_0.5?x Ag_1.5?y In _x+y Se and Se as contaminant phases.