Differential Buffer Research Articles

A fully differential CMOS line driver for ISDN

A CMOS differential buffer amplifier for ISDN applications is discussed. The chip operates from a single 5-V power supply and can deliver a 6-V (peak-to-peak), 80 kHz signal into a load of 100 Omega and/or 300 pF with a total harmonic distortion (THD) of about 0.25%. The amplifier's main feature is its power supply rejection ratio, which remains practically constant at -75 dB from DC to several hundred kilohertz for both positive and negative supplies with the common-mode voltage generated on chip. In an inverting configuration with a gain of 1.5, the 1% setting time for step input is less than 500 ns for a step of 1.5 V and less than 1 mu s for a step of 6 V (for both cases, the output load is 100 Omega and 300 pF). By using relatively small devices for the output stage, the amplifier occupies an area of only 1400 mil/sup 2/ in a 2- mu m double-poly single-metal n-well CMOS technology. >

An 8-bit 2-ns monolithic DAC

An 8-bit resolution ultrahigh-speed monolithic digital-to-analog converter (DAC) is fabricated using super self-aligned process technology. In order to improve dynamic accuracy, which is determined by settling speed, clock feedthrough noise, and glitch, a number of circuit technologies are developed including a rise- and fall-time control switch driver, a low-noise flip-flop, and a differential buffer configuration. In addition, a chip assembly technology using a multilayer ceramic substrate is developed. The DAC exhibits a settling time to 8-bit accuracy of about 2 ns, a maximum conversion rate of 1 GHz, a glitch energy of 2 ps-V, and a 10-bit linearity error accuracy without trimming.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Differential potassium buffer behavior of individual soils related to potassium corrective treatments

Abstract Although the basic chemistry and behavior of potassium in the soil is well understood, little of this knowledge is used in soil testing and practical soil fertility mangement. In this study the K buffer behavior of three individual soils (Hagerstown silt loam (Typic Hapludalf), Gatesburg sand (Entic Haplorthod) and Gilpin channery silt loam (Typic Hapludult)) was investigated. The buffer relationships determined indicated very different K behavior for these soils even though exchangeable K soil tests indicated similar K levels. It was also determined that for these soils the buffer relationship was apparently independent of previous K management, indicating that the K buffer behavior could be included as part of soil characterization data. The role of nonexchangeable K in determining K buffer behavior was also investigated. It was found that the levels of solution K where the release of nonexchangeable K becomes measurable (0.27 ‐ 0.83 × 10‐4 M) are similar to solution K levels reportedly required for crop growth (0.02 ‐ 0.95 × 10‐4 M). It was also found that these soils were capable of maintaining a relatively high level of exchangeable K even after extraction of significant amounts of nonexchangeable K with sodium tetraphenyl boron. It was concluded that K buffering behavior of individual soils could and should be included in K management decisions involving corrective soil treatments and/or crop removal estimation. Otherwise, based on current soil tests, soils with very different K buffer behavior will be treated similarly.

Acid‐ and base titration behaviour of finnish mineral soils

AbstractThe acid‐ and base‐buffering properties of 84 non‐calcareous surface soil samples were studied by batch titration with HCI or KOH at a constant ionic strength of I = 0.1. The soil samples were classified according to their pH of zero point of titration (ZPT). Differential buffer values, dB(H) or dB(OH) (H+ or OH− as meq kg−1 needed to reduce or increase the soil pH sequentially by 0.5 units, respectively), were introduced to describe the course of titration curve and the intensity of buffer action.In all soils, the first acid‐buffer value, dB(H)0→0.5, varied from 8 to 78 meq kg−1 and the second one, dB(H)0.5→1, from 10 to 138 meq kg−1. The corresponding base‐buffer values, dB(OH)0→0.5 and dB(OH)0.5→1, ranged from 10 to 48 and from 14 to 44 meq kg−1, respectively. The most acid soils were most strongly buffered against acid, and the soils with the highest initial pH against base. The results reveal the acid‐buffering by exchange reactions to be very important. In the soils with ZPT≦5.4, the first acid‐buffer value was dependent on the content of organic matter and oxalate‐soluble Al, whereas in the more acid soils the role of clay became significant. Thus, it was concluded that at higher pHs the foremost inactivation of H+ is attributable to soil components of pH‐dependent charges, and the significance of constituents of permanent charges to increase with proceeding acidification. In strongly acid soils (ZPT≦4.8) the very effective buffering seemed to be primarily due to the dissolution of Al‐hydroxides and, thus, to exert detrimental effects on the edaphic environment. The general rank of soil factors explaining the variation in the base‐buffer values was in accord with the neutralization sequence, i.e. the strongest acid in the soil being neutralized first. In the strongly acid soils (ZPT≦4.8) the base‐buffer values seemed to depend on the clay as well as KCl‐ and NH4OAc‐extractable Al, whereas in the soils with higher initial pH mostly on organic C.

Scrapie: concept of a virus-induced amyloidosis of the brain.

After an intraperitoneal infection disease-specific incorporation of [3H]leucine into protein and [3H]uridine into RNA in the brain precede clinical scrapie in hamsters. Onset of both incorporations are the earliest measurable events in the disease. Infectivity and subsequent clinical symptoms appear only after this biochemical activity has ceased. The disease-specific [3H]protein co-purifies with scrapie-associated fibrils (SAF) and infectivity during differential centrifugation and buffer extraction. SDS-PAGE shows that the [3H]protein is not SAF protein but a protein with an apparently higher mol. wt. The [3H]RNA is metabolically stable and separates from SAF and the main portion of infectivity in the last step of the purification. The appearance of SAF-protein is a late event and correlates with severe clinical symptoms. SAF seems to be derived from a brain protein turning over slowly. Our data are consistent with early pre-clinical virus replication. In this case treatment aimed at suppressing virus replication in the clinical phase of the human Creutzfeldt-Jakob disease is unlikely to produce any beneficial effect.

Potassium additions on ionic equilibria, selectivity and diffusion of cations in soils

Abstract In a soil system variation in the concentration of any one ion as induced by external addition might bring changes in the ionic‐equilibria, diffusion rate and strength of adsorption of all the ions involved. In four Indiana soils the changes in ionic equilibria, selectivity coefficient and rate of diffusion coefficient for K, Na, Ca and Mg were investigated at 5 levels of added K. The experiments were carried out under controlled laboratory conditions by incubating soils for 3 weeks at 25C. All soils had a greater fraction of Ca and Mg on the exchange phase than in solution, whereas with K and Na the reverse occurred. Potassium adsorption isotherms for all the soils differed indicating the difference in the nature of soil materials involved. Chalmers soil with high clay content with high exchange capacity had high differential buffer value for K. In all the soils, K was adsorbed preferentially to Na at all the levels of K addition, Calcium was adsorbed preferentially to Mg on the Zanesville and T...

Radiolabeling of platelets

The radiolabeling of platelets has been studied for many years, both with megakaryocytes labeled in vivo and with direct platelet labels in vitro. The major aim of this work has been to evaluate platelet interactions in vivo. This has been made possible with indium-111-labeled platelets. The radionuclide is easily imaged and can be incorporated into platelets with ease. Unfortunately, the lipophilic complex used is not platelet-specific and must be exposed only to the isolated cell population for specific labeling. This requires isolation of platelets from whole blood followed by one of many variations of differential centrifugation, buffer washes, and resuspension techniques that have been reported. The major differences in these techniques are the resuspension media, the incubation time, and the ligand used. These variations are discussed with emphasis on known platelet characteristics and specific responses to these modifications.

A field emission e-beam system for nanometer lithography

Field emitters offer a particularly high potential in e-beam lithography when writing in the nanometer range. Using a modified VG Microscopes Ltd., model HB 501 STEM, a current of 0.1 nA can be focused into a diameter of 2.5 nm at 100 kV with a final beam aperture of 1.6 mrad. In order to fulfill the demands of microlithography, an objective lens of 15 mm nominal focal length is used. Stage travel in the system is 5 mm in the X and Y directions and the maximum scan field is 250×250 μm2. The beam is deflected electromagnetically under computer control and vector scanning is used during lithography. The 14 bit digital pattern generator has been electrically isolated by optocouplers from the host computer and is connected via analog differential buffers to the deflection amplifiers. The cold tungsten field emitter exhibits a linear decrease in current of about 20% within 20 min of continuous writing. The decrease in current is corrected during lithography by a feedback to the clock frequency of the digital pattern generator to maintain a constant exposure dose. The high current available enables the use of organic resists as well as low sensitivity inorganic resists such as NaCl or WO3. So far 10 nm resolution has been achieved by in situ vaporization of NaCl.

Serum Cholinesterase Variants: Examination of Several Differential Inhibitors, Salts, and Buffers Used to Measure Enzyme Activity

Abstract Dibucaine, used as a differential inhibitor with acetyl-, propionyl-, and butyrylthiocholine as substrate, clearly identified the "usual" and "atypical" serum cholinesterases. Succinylcholine was also used successfully as a differential inhibitor with butyrylthiocholine as substrate. Sodium fluoride, used as a differential inhibitor, gave conflicting results, depending on whether Tris or phosphate buffer was used in the assay. Mono- and divalent cations (NaCl, KCl, MgCl2, CaCl2, and BaCl2) activated the "usual" and inhibited the "atypical" enzyme at low concentrations. The "usual" enzyme had the same activity in 0.05 mol of Tris or phosphate buffer per liter, while the heterozygous and "atypical" enzymes showed 12 and 42% inhibition, respectively, when assayed in the phosphate buffer. Kinetic studies showed the phosphate acted as a competitive inhibitor of "atypical" enzyme. Km values, determined for "usual" and "atypical" enzymes, were 0.057 and 0.226 mmol/liter, respectively, with butyrylthiocholine as substrate.