Differential-difference amplifier

C. Hung, M. Ismail, K. Halonen, and V. Porra, Low-Voltage RaU-to-RaU CMOS Differential Difference Amplifier , Proc. IEEE International Symposium on Circuits and Systems, Vol. 1 (1997), 145-148. 

In principle any voltage difference amplifier, including an ideal operational amplifier, produces an output that is proportional only to the differential voltage K+ — F and is independent of the co/nmon-znof/e vo/ a e [CMV = V+ + IT)]. The extent to which this is true of a real amplifier can be judged by the common mode rejection ratio ... 

In the differential-temperature loop, signals representing the sample and reference temperatures, as measured by the platinum-resistance thermometers, are fed to the differential-temperature amplifier via a comparator circuit, which determines whether the reference or the sample temperature is greater. The differential-temperature-amplifier output then adjusts the differential-power increment put into the reference and sample heaters in the direction and magnitude necessary to correct any temperature difference between them. A signal proportional to the differential power is also transmitted to the pen of a recorder, giving a curve of differential power versus time (temperature). The area under a peak, then, is directly proportional to the heat energy absorbed or liberated in the transition,... 

The process flow for the fabrication of the microfluidic system includes a single or double metallization layer, a polymer layer for the fluidic system, and a glass sealing cap. There have been some efforts during fabrication to minimize the thermal-dissipation loss. The temperature difference between the two points where the sensors are located is measured with a differential current amplifier, and the flow rate is calibrated. At low flow rates, the temperature difference is a linear function of the flow rate as in Fig. 6. Measurements without heat insulation decrease the sensitivity of the flow sensor and increase the lower limit of flow rate detection. The distance between the heater and the sensors is optimized for the maximum differential temperature. 

The induced body potential is present at both inputs of a difference amplifier, and as used here, it is also known as the common-mode potential This is so because it is common (equal) in amplitude and phase at each of the two amplifier inputs. Thus, for our differential anqilifier. 

The difference amplifier shown in Figure 27.8 is a basic amplifier block that can be extended to measure very small signals differentially in the body. Such measurements are the basis behind common connected health signal-acquisition targets such as the electrical activity of the heart (EKG/ECG), those of the muscles (EMG), and that... 

Closing the differential temperature amplifier loop leads to the final measuring configuration. Equation (1) applies, as before, and Eq. (4) is identical to Eq. (2), but Eq. (3) must be replaced by Eq. (5). The heat flow into the sample has an additional contribution, that represents the heat flow from the differential temperature loop. The value of Wp (in J/s, or watts) is proportional to the recorded temperature difference signal,... 

One additional point needs to be considered. The commercial DSC is constructed in a slightly different fashion than that just described. Rather than letting the differential amplifier loop correct only the temperature of the sample, an equal amount of power is subtracted from or added to the power delivered to the reference by the average temperature amplifier. This is accomplished by proper phasing of the power input of the differential temperature amplifier. In reality, thus, one-half of is added to the sample calorimeter in addition to the full power from the average temperature loop, while one-half of IFp is at the same time subtracted from the power going into the reference calorimeter. This results in a total additional power to the sample that is equal to IV, as required by our calculations. The performance of the DSC is thus still described by Eqs. (1), (4), (5), (10), and (11). 

Rectifiers working according to the control diagram in Fig. 8-6 are used for anodic corrosion protection in passivatable systems that go spontaneously from the passive to the active state when the protection current is switched off [12]. The predetermined nominal voltage between reference electrode and protected object is compared with the actual voltage f/j in a differential display unit D. The difference AU = is amplified in a voltage amplifier SV to VqAU. This... 

Differential display is a method for identifying differentially expressed genes, using anchored oligo-dT, random oligonucleotide primers and polymerase chain reaction on reverse-transcribed RNA from different cell populations. The amplified complementary DNAs are displayed and comparisons are drawn between the different cell populations. 

Fig. 19.1 Differential displays comparing RNAs from saline (S)-, imipramine (I)- or fluoxetine (F)-treated rats. Total RNA was extracted from hypothalami of animals treated with the different drugs for two months. Autoradiograms of amplified -[35S]-dATP-labeled PCR (polymerase chain reaction) products after electrophoresis in 6% polyacrylamide gels are shown for two different primer combinations that identified one upregulated (arrowhead) and one downregulated (arrow) fragment in the groups treated with antidepressants (from [4] with permission).

The key point of our transistor model is the negative differential heat resistance as we observed in the diode model(Li Wang Casati, 2004). It provides the possibility that when Ta changes both Js and Jd change simultaneously in the same way. Therefore Js = Jd (or Js Jd) can be achieved for several different values of T0 or even in a wide region of T0 as shown in Figs.10 and 11. In this situation heat switch and heat modulator/amplifier are possible. In the ideal, limiting... 

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