This paper presents the results from an investigation on the implementation of Current Mode Instrumentation Amplifiers (CMIAs) with rail-to-rail operational amplifiers (op amp) with a gm control circuit. The objective of employing rail-to-rail op amps in the implementation of a CMIA is the improvement of the common-mode operation range. The enhancement of the input common mode range (ICMR) is obtained using op amps with a rail-to-rail input stage followed by a cascode-based output stage. A prototype of the CMIA was implemented in standard 0.6 lm XFAB CMOS technology. Test results showed that the CMIA common mode range was extended but with moderated CMRR. To minimize this issue the amplifier was re-designed and sent to fabrication. Simulations with the components variations included were performed and showed the enhancement of the CMRR can be expected.
A Current Mode Instrumentation Amplifier with rail-to-rail input and output is presented. It is based on constant gm input stages, and cascode output stages. Although this CMIA structure has a good Input Common Mode Voltage, it suffers from a poor output swing, due to the limitation imposed by the current mirrors. This problem is overcome by using a transconductance amplifier as output block. The circuit was designed to 0.6µm XC06 XFAB CMOS technology. Post layout simulations on the extracted circuit net-list provide a bandwidth about 70 kHz (-3dB), and a CMRR higher than 160dB, for a dc gain set to 66 dB. The power consumption is 149µW at ±1.5V.
We perform molecular dynamics simulations
in order to
study thermodynamics
and the structure of supercooled aqueous solutions of lithium chloride
(LiCl) at concentrations c = 0.678 and 2.034 mol/kg.
We model the solvent using the TIP4P/2005 potential and the ions using
the Madrid-2019 force field, a force field particularly suited for
studying this solution. We find that, for c = 0.678
mol/kg, the behavior of the equation of state, studied in the P–T plane, indicates the presence
of a liquid–liquid phase transition, similar to what was previously
found for bulk water. We estimate the position of the liquid–liquid
critical point to be at T
c ≈ 174
K, P
c ≈ 1775 bar, and ρc ≈ 1.065 g/cm3. When the concentration is
tripled to c = 2.034 mol/kg, no critical point is
observed, indicating its possible disappearance at this concentration.
We also study the water–water and water–ions structure
in the two solutions, and we find that at the concentrations examined
the effect of ions on the water–water structure is not strong,
and all the features found in bulk water are preserved. We also calculate
the hydration number of the Li and Cl ions, and in line with experiments,
we find the value of 4 for Li+ and between 5.5 and 6 for
Cl–, confirming the good performances of the Madrid-2019
force field.
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