Control current sources

HII1T Gl is a voltage-controlled current source. The current through Gl is 0.5 times the voltage Vx. Note that Vx is the voltage at node V2 minus the voltage at node V3. It is not necessary to add the text Vx to your circuit. 

In general, controlled-current electrolyses need less expensive equipment. Only a controlled-current source in combination with a coulomb integrator is necessary. Therefore, in industry, electroorganic reactions are always performed at a fixed current density. In the laboratory, it is advisable to start with controlled-potential electrolyses using a potentiostat and a three-electrode electrolysis cell (Fig. 22.8). In this way, the reaction can be controlled at the redox potential of the substrate determined analytically, and the selectivity of the process can be studied at different potentials. After determination of the selectivity controlling factors, it is usually possible to change over to current control by proper selection of the current density and the concentration of the substrate. Using a continuous process, the concentration can be fixed at the desired value. Thus, selectivity can also be obtained under these conditions. 

Current feedback amplifiers always consist of a diamond transistor (DT) and a buffer stage internally connected. The OPA660 [42] or its replacement OPA860 [43] allows separated access to both circuit parts so that a voltage-controlled current source (OTA) at a bandwidth of 90 MHz and a buffer stage at a bandwidth of 700 MHz are available. In contrast to normal transistors the diamond transistor, whose temperature-stabile operating point is internally determined, allows four-quadrant operation. The OTA provides the required almost-ideal transistor to design an emitter-coupled oscillator. 

Ideally, the drive TFT would be a perfect voltage-controlled current source in which the current delivered to the OLED is a function of the data voltage alone, and this function is nniform across the display. Even if the current is a complicated nonlinear function of the data voltage, this fnnction can be determined in advance and the data can be warped to take the nonlinearity into account. Unfortunately, the current is... 

FIGURE 23 Circuit schematic symbol for (a) voltage-controlled voltage source (VCVS), (b) current-controlled voltage source (CCVS), (c) voltage-controlled current source (VCCS), (d) current-controlled current source (CCCS). 

The two types of dependent current sources are diagrammed symbolically in Fig. 2.3(c) and Fig. 2.3(d). Figure 2.3(c) depicts a voltage-controlled current source (VCCS), for which the controlled current io t) flowing in the electrical path from terminal 3 to terminal 4 is determined by the controlling voltage v, (t) established across terminals 1 and 2. The controlled current can, therefore, be written as... 

FIGURE 7.50 The Class A amplifier transistor can be modeled as a current controlled current source with internal output resistance R. When R = Rl, half of the collector power is dissipated in R and the other half in Ri, providing a maximum efficiency ijmax of 50%. This agrees with Eq. (7.31). Not shown are the matching circuits transforming r e and Rl to a standard impedance, such as 50 2. 

FIGURE 7.56 The nonsaturated Class C amplifier may be modeled as a current controlled current source with a measurable input resistance when driven, and an internal output resistance determined by the power efficiency, ij Rmt shares power with J sl> but Rint oo when ij... 

To construct N given N, voltage-controlled-voltage-sources in N are replaced by current-controlled-current-sources in N with input terminal pairs of the sources exchanged with output terminal pairs as shown in Fig. 7.147. Passive elements R,L, and C are left unchanged. The resulting networks are termed... 

FIGURE 7.147 Voltage-controlled-voltage-sources are replaced by current-controlled-current-sources with input and output terminal pairs exchanged to obtain N from given network N. 

A measurement setup is build to verify the calculated production of gas during electrolysis according to eq 9. A computer controlled current source (CCCS) is used for electrolysis. The current source is equipped with two current ranges, 0-100 pA and 0-2 mA. The connection holes of the reservoirs are sealed with epoxy (Araldit). The calibration system is then immersed in an electrolyte solution. The electrolyte consists of a 200 mM KNO3 solution to which some detergent (Tween 20) is added. Using a vacuum system, air inside the calibration system is replaced by the electrolyte solution. 

Figure 12. The measurement set-up, consisting of a computer controlled current source (cccs) to evoke gas bubbles by electrolysis and a ccd camera to monitor the fluid displacement.

Macias R, Seoatte F arxl Bragos R. (2010) Performattce of the Load-in-the-Loop Single Op-Amp Voltage Controlled Current Source from the Op-Amp Parameters. International Conferettce on Electrical Bioitnpedance lOP Publishing Journal of Physics Conference Series 224... 

With continued smdies, we were able to show that the ES ion source, as depicted in Figure 3.1, operates electrochemically in a fashion analogous to that of a conventional controlled-current electrochemistry (CCE) flow cell." A conventional CCE flow cell houses a working electrode, a counter electrode, and a controlled-current source to set the magnitude of the current through the cell— that is, the cell current, In our view,... 

The capillary with flowing solution acts as a current source 5 incorporated into electric circuit using two Ag/AgCl electrodes. Another voltage-controlling current source 6 is also included into the circuit. This enables the complete electrical characteristic of a solution in the capillary, i.e., the dependence of the potential difference E across the capillary ends on the current I to be obtained. 

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