AB Amplifier

A class AB amplifier is defined as an amplifier using a power stage that has output current flow for more than half, but less than all, of the input cycle (Gilbilisco 1994). 

Three different measurements were made in order to characterize the performance of this amplifier circuit and show the correlation of the breadboard results to the SPICE models. The three inputs and their resulting measurements are described in detail in Table 6.1. 

A 1 kHz sine wave was provided at the input, and the output result was measured. The breadboard results are shown in Fig. 6.23. The top trace is the output waveform. The bottom trace is the input waveform. 

TABLE 6.1 Characteristic Measurements Made on Class AB Amplifier Circuit 

VIN PULSE -100M 100M 0 100N 100N 50U 100U 

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In order to measure the frequency response of the class AB amplifier, the input voltage source was changed to a small-signal AC stimulus source (AC 1). The breadboard results are shown in Fig. 6.31. The IsSpice, PSpice, and Micro-Cap results are shown in Figs. 6.32, 6.33, and 6.34, respectively. 

The rf transmitter amplifies an rf pulse signal of about 1 mW up to several W or up to several kW. The amplifier should work in a linear mode (class AB) because excitation pulse shape for slice selection must be reproduced. Class AB rf transmitters such as these with blanking gates are widely available commercially. 

The main drawback of the galvanometer-spot follower system is that the sensitivity level of the line is defined ab initio and cannot be modified except by increasing or decreasing the number of thermoelements in the circuit. A more versatile, but more expensive, system is provided by the addition of a dc amplifier to a recording voltmeter. 

Figure 6.18 ImmunoRCA Assay. Top left A reporter Ab conjugated to an oligonucleotide binds to a test analyte captured on a solid surface by a covalent attachment or by a capture Ab. Top right DNA circle hybridizes to a complementary sequence in the oligonucleotide. Bottom left Resulting complex is washed to remove excess reagents, and the DNA tag is amplified by RCA. Bottom right Amplified product is labeled in situ by hybridization with fluor-labeled oligonucleotides. (From Schweitzer, B. et al, Proc. Natl. Acad. Sci. USA, 97, 10113-10119, 2000. With permission.)...

Messenger RNA is isolated from the tissue source selected to contain the Ab-secreting cells. Spleen, bone marrow, tonsil, and lymph node have all been successfully used as a source Copy DNA (cDNA) is then generated by reverse transcription and Fv or Fab regions amplified by PCR. 

Wey AB, Zhang C-X, Thormann W. Head-column field-amplified sample stacking in binary system capillary electrophoresis. Preparation of extract for determination of opioids in microliter amounts of body fluids. J Chromatogr A 1999 853 95. 

The practice of weighting variables by the reciprocal of their standard deviation is common in many applications, especially where the variables have different units. In contrast this is seldom used in spectroscopy calibration, because the variable are of die same type and units, and information is usually considered to be related to broader peaks (4). A preliminary trial showed that X-variable standardization amplified e noise of the PLS model (data not shown). Since the 436 X-variables are all in the same units (ABS 520 nm) with presumably similar noise levels, they were not weighted. The Y-variables were also be kept unweighted, since the relative noise levels between X and Y variables are more or less irrelevant (S). 

Solution resistances were measured at 1000 Hz with an AC Wheatstone bridge an HP 200 AB oscillator provided the input and a tuned amplifier with a null detector was used to find the bridge balance (with simultaneous resistance and capacitance balancing). A homemade cell with Pt electrodes was used, similar to the one described in Ref. 27a. The cell was calibrated with 0.10N NaCl solutions. 

Baker B (1996) Tuning in amplifiers (AB-105). Burr-Brown, Tucson... 

The first SPR immunosensor for detection of pesticides was developed by Mimmni et al. [22] in the early 1990s. They used an SPR sensor developed by Biacore AB, Sweden, with the atrazine derivative bound to dextran matrix on the sensor chip. The detection of atrazine was performed using the inhibition assay and monoclonal antibodies. The sensor response was subsequently amplified by secondary antibody, which was bound to the antibody captured by the atrazine derivative (sandwich assay, see Chap. 7 in this volume [54]). This biosensor was demonstrated to measure atrazine in distilled and tap water within the range 0.05-1 ng mL in 15 min and exhibited relatively low crossreactivity with simazine and tetrabutyl atrazine (20%). The sensor surface was regenerated with 100 mM sodium hydroxide in 20% acetonitrile. 

Figure 14. Schematic diagram of the CO metastable TOF experimental apparatus is shown. The molecular beam (MB) containing 10% ketene in neon or helium can be placed at any acute angle (0,ab) relative to the flight path, and it is collimated by an electroformed skimmer (not shown). The photolysis laser is an unpolarized excimer (XeCl or XeF), and the probe laser is a pulse dye amplification system whose polarization can be made either parallel (sPR, ) or perpendicular (e ) to the flight path. The metastables pass through a 1-cm orifice and deflector plates and grids (both not shown), and they strike a heated Ni surface. Electrons produced from the Ni surface by the metastables are steered by a plate set at —1500 V onto a stack of 3 MCPs the resulting pulses are then amplified, discriminated against noise from dark current, and counted by a multichannel scaler.

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