Fixed bias

Fig. 3 Principle of electrolyte gating. Tuning of the Fermi levels of WEI and WE2 relative to the molecular levels enables measuring of current (0-voltage (E) characteristics i vs ( wei -L we2) at fixed wei or we2, i vs wei or we2 at fixed bias Ebias = ( wei -Ewe2> as well as barrier height profiles i vs distance z of tailored molecular junctions in a vertical SPM-based configuration respective horizontal nanoelectrode assembly...

Figure 11.10. NW smart pixels, (a) Schematic of an integrated crossed NW FET and LED and the equivalent circuit, (b) Shows SEM image of a representative device, (c) Plots of current and emission intensity of the nanoLED as a function of voltage apphed to the NW gate at a fixed bias of -6V. (d) EL intensity versus time relation when a voltage applied to NW gate is switched between 0 and +4V for a fixed bias of -6V. [Reprinted with permission from Ref. 59. Copyright 2005 Wiley-VCH Verlag.]...

The proportional controller is unable to return the controlled variable to the set point following the step load change, as a deviation is required to sustain its output at a value different from its fixed bias b. The amount of proportional offset produced as a fraction of the uncontrolled offset is 1/(1 + KK ), where K is the steady-state process... 

The observations illustrate that inelastic and thermally activated tunnel channels may apply to metalloproteins and large transition metal complexes. The channels hold perspectives for mapping protein structure, adsorption and electronic function at metallic surfaces. One observation regarding the latter is, for example that the two electrode potentials can be varied in parallel, relative to a common reference electrode potential, at fixed bias potential. This is equivalent to taking the local redox level up or down relative to the Fermi levels (Fig. 5.6a). If both electrode potentials are shifted negatively, and the redox level is empty (oxidized), then the current at first rises. It reaches a maximum, convoluted with the bias potential between the two Fermi levels, and then drops as further potential variation takes the redox level below the Fermi level of the positively biased electrode. The relation between such current-voltage patterns and other three-level processes, such as molecular resonance Raman scattering [76], has been discussed [38]. 

The following is an example of a mathematical/statistical calculation of a calibration curve to test for true slope, residual standard deviation, confidence interval and correlation coefficient of a curve for a fixed or relative bias. A fixed bias means that all measurements are exhibiting an error of constant value. A relative bias means that the systematic error is proportional to the concentration being measured i.e. a constant proportional increase with increasing concentration. 

The equation for the best fit straight line from these calculated values is y = —0.028 + 1.0114x. This equation suggests that a constant error of —0.028 is evident regardless of the true concentration and this is a fixed bias of —0.028 and a relative bias of 1.14%. Using these figures it is possible to calculate the bias at any particular concentration. 

The relative bias gives an error of —0.0223% for 0.5 ppm vanadium and 0.086% for 10.0 ppm vanadium metal and this shows that the relative bias exerts a greater influence on the determination than does the fixed bias (see Table 3.7). The estimated error due to relative bias is calculated by taking differences between 1.0114 and 1.000 of the perfect line and correcting for each concentration is used to calculate each predicted concentration. Table 3.7 gives results obtained along with each residual. 

True cone. Estim. error fixed bias Estim. error rel. bias (0.0114x) Estim. total error due to bias Predicted cone. Measured cone. Residual Residual [2]... 

The true intercept is 95% confidently between —0.098 and 0.042 and since this interval includes zero therefore it may be possible that no fixed bias is evident. The confidence interval, the true slope b of a regression line, is given by ... 

The calculation above was unable to prove whether a fixed bias exists and the best way to estimate this is to fit the equation y = bx forcing a zero intercept (Table 3.8). 

Device measurement can be performed after the device is held at a fixed bias for some time this will expose the direction and nature of the hysteresis. The IEEE 1620 standard recommends 10 minutes at Vos = Vds = OH. Holding the device at a high bias before measurement can also be used to measure the complementary effect. 

Region 111 is more pronounced developed for the slightly thicker and more densely packed (25%) BPS adlayer, as compared to BP4. The tilt angle of the biphenyl moiety, as referred to the surface normal, is significantly smaller for the former. This is also reflected in the observation that, in constant current mode and at a fixed bias potential, the absolute tip-substrate distance z appears to be slightly larger in the presence of BPS. Similar trends were also observed for the other BPn molecifles (n = 2-6). 

A fixed bias ( )(. exists when the magnitude is independent of the level or value of the measured property. 

If only one reference material is available, the bias can be evaluated only at the level of the reference material. Since both relative and fixed bias may be present, this bias is designated as composite bias, and it is given in absolute terms by... 

Estimated values for the slope a and the intercept h are obtained by way of regression calculations as given in Section 6.5. The fixed bias (B)p is equal to h. and the relative bias (B)n is equal to o - I. The composite bias is given by... 

To test the time response of the sensors, a 10% H2/90% Nj ambient was switched into the chamber through a mass flow controller for periods of 10,20 or 30 s and then switched back to pure Nj, Figure 5.9 shows the time dependence of forward current at a fixed bias of 2V under these conditions. The response of the sensor is rapid (< 1 s), with saturation taking close to 30 s. On switching off the hydrogen-containing ambient, the forward current decays exponentially back to its initial value. This time constant is determined by the transport properties of the test chamber and is not limited by the response of the diode itself. 

Time response at 25°C of a MOS-HEMT-based diode forward current at a fixed bias of 2 V when switching the ambient from Nj to 10% H2/90% Nj for periods of 10, 20 or 30 s and then back to pure Nj. 

Variation in forward current at fixed bias for diodes with boride-based ohmic contacts (upper trace) or conventional ohmic contacts (lower trace) as a function of time under field conditions where the temperature increases during the day and decreases at night. 

Typical Operating Conditions (class A amplifier) Fixed bias Cathode bias... 

FIGURE 5.13 Triode audio amplifier circuits (a) audio amplifier with fixed bias, (b) audio amplifier with cathode bias (self-bias). 

---