Passive circuits

In practice, we cannot build a pneumatic device or a passive circuit which provides ideal derivative action. Commercial (real ) PD controllers are designed on the basis of a lead-lag element ... 

The technique presented here can be used to measure the impedance or resistance between any two nodes. We will find the AC impedance between two nodes. We will illustrate using two examples. The first will be a passive circuit with resistors only. The second will be a jFET source follower. 

The mathematical expressions which describe the impedance of some passive circuits are shown below, where a passive circuit is one that does not generate current or potential [129], In this regard, the impedance response of simple passive circuit elements, such as a pure resistor with resistance R, a pure capacitor with capacitance C, and a pure inductor with inductance L, are given, respectively ... 

The extreme thermodynamic model of passive circuit (without effective pressure sources) is obtained by transforming model (13)—(17). Toward this end let us mentally isolate a passive fragment with np... 

Passive circuit elements are components that do not generate current or potential. A passive electrical circuit is composed only of passive elements. Only an element with two contacts is considered here, which is analyzed by considering the current flowing through and the potential difference between the contacts, shown as open circles in Figure 4.1. 

The varied devices previously discussed may be combined with other active or passive circuit elements to make integrated circuits. The major of ICs using III-V materials are Digital ICs, monolithic microwave integrated circuits (MMICs) and opto-electronic integrated circuits (OEICs). 

When the equivalent circuit is suitable it can be treated as a passive circuit in that no differential equations need to be solved for the currents or voltages in the circuit. The only differential equation associated with the circuit is the torque necessary to accelerate the rotor and its coupled load. For this purpose the standard form of equations for the electrical torque are appropriate, in which the air-gap voltage V , should be used. 

One of the exceptions to shape based engineering objects is an electronic system where active and passive circuit elements are connected by routes but not in a dimensioned space. However, this model of an electronic system is completed with shape models of printed circuit board arrangements and programming of automatic assembly and inspection equipment. At automatic assembly, circuit elements R31, R33, and C33 should be positioned relative to the printed circuit board (Figure 1-4). At automatic inspection, a camera image of the ready assembled printed circuit board is compared with a master image to reveal parts omitted during assembly. 

We are all familiar with the classic, passive circuit components resistor, capacitor, and inductor. In a 1971 paper, however, Leon Chua argued that there was room for a fourth basic component, which he called memristor, short for memory resistor (Chua, 1971). The memristor is a special kind of resistor in which the resistance is dependent on the net amount of charge having passed through it. Hence, sending a current in one direction... 

For all-printed thin film transistors (TFT), various organic and inorganic metal electrode materials, such as conductive polymer, carbon nanotube (CNT), organic metal compound, or metal nano-particles, have been used as gate and source/drain electrodes [6-11] in a combination with inkjet- and laser-based printing methods. One of the immediate applications for all-printed TFT would be flexible or rugged display backplane and disposable radio frequency identification (RFID) tags. In addition, printed metal electrodes and TFT have also been used to fabricate passive circuit components, power transmission sheets and sensors for ambient electronics and electronic skin [12-13]. 

System with negative resistance cannot be represented by a passive circuit with positive R, L, and C elements. The stability criterion demands that there be no negative impedances in the system (mle 3 of Kramers-Kronig conditions). For example, the system shown in Fig. 13.1 contains negative resistance, and its impedance is not transformable. However, Kramer-Kronig transforms can also be applied to admittances. Admittance calculated for this case is also shown in Fig. 13.1, and it is perfectly Kramers-Kronig transformable. Moreover, infinite impedance corresponds to zero admittance which is transformable. This topic will be further discussed in Sect. 13.3.4. 

In the analysis of behavior of passive circuits they can be considered as "fragments" of active ones. Thus, the passive scheme that includes independent loops 2342, 2352 and 24152 can be obtained by removing from the scheme of Fig. 3,a the branch 1-2 with motive pressure and setting the source at node 2 and the sink at node 1, each being equal to the flow in the removed branch. The flow distribution for such a scheme will be determined from the model ... 

A filter is, in the context of fhis discussion, an electrical circuit which alters the spectral composition of the signal upon which it operates. Filters are usually used to attenuate unwanted spectral ranges, although they can also be used to increase signal power in specific bands. Sometimes both are required. Filters can take the form of single passive circuits containing few elements to complex systems requiring sophisticated analysis to model fully. 

The monthly journals IEEE Transactions on Miaowave Theory Techniques, IEEE Microwave and Guided Wave Letters, andlEEE Transactions on Antennas and Propagation publish articles on modeling and design of microwave passive circuit components. Articles in the first two journals are more circuit and component oriented, whereas the third focuses on field theoretic analysis. These are published by the Institute of Electrical and Electronics Engineers, Inc. For subscription or ordering contact IEEE Service Center, 445 Hoes Lane, P.O. Box 1331, Piscataway, NI 08855-1331. 

Passive circuit realizations of filters have very low sensitivities to element values. Lossless filters designed to maximize power transfer between source and load have the lowest possible sensitivities in the passband (Schaumann, Ghausi, and Laker, 1990). These networks are realized as double-terminated LC ladders as shown in Fig. 7.107, and the corresponding active hlter realizations based on ladder simulations begin with the passive hlter schematic rather than with the transfer function. 

Figure 1.82 shows the model circuit which takes the form of a diagonally connected discrete ladder network or in simple terms, a dual-rail transmission line of finite dimension. The essential problem is to replace the general impedance elements x, y, and z by suitably arranging such passive circuit elements as resistors and capacitors that adequately represent the microscopic physics occurring within an electronically conducting polymer. 

The active balance circuit is more complex than the passive circuit. It generally comprises an electronic power circuit, placed in parallel with the supercapacitor. It is able to divert the current when the voltage of the supercapacitor is in the vicinity of the maximum acceptable voltage. The main drawback to this circuit is its very high cost (practically as much as the supercapacitor itself). 

Noise produced in passive circuit elements (resistors especially) is usually of thermal origin and has the mean-square voltage value... 

A circuit test vehicle with both active and passive elements was designed (Ref 44). The passive circuits consisted of band pass filters (6 to 7 GHz range) and T-resonators (5, 10, and 15 GHz), while the active circuits included a mixer device (4 to 6.5 GHz), a VCO module and a wide-band amplifier circuit. The assemblies were tested after soldering and reflow, and again after flux/paste residues had been removed. Variations in signal transmission for two different solder pastes were observed on the passive circuit elements. For the mixer device, variation between signal transmissions for the measurements with/without paste residues was approximately 1%. 

Since electrons are negative, a positive value of E means that the chemical potential of the electron is larger in the left electrode. If a passive circuit (one that does not exert its own voltage) is connected between the terminals, electrons will move spontaneously from the left terminal to the right terminal through this circuit. The cell reaction proceeds spontaneously in the direetion in which we wrote it. If E is negative, the reverse of the cell reaction proceeds spontaneously and electrons move spontaneously from right to left in the external circuit. 

This quantity is the same as the activity quotient of Chapter 7. If the reaction takes place outside of an electrochemical cell, Q will tend toward its equilibrium value. If the reaction takes place in an electrochemical cell, Q can take on other values at equilibrium. If a passive circuit is connected, the reaction will tend toward the same equilibrium that would occur outside of the cell. If a counter voltage is applied by an external circuit, the equilibrium state will depend on the value of the counter e.m.f., and at equilibrium E will be equal to the counter e.m.f. If all substances are in their standard states, all activities are equal to unity, and Q is equal to unity. In this case we obtain the important equation... 

Since E > 0, the reaction would proceed spontaneously as written in the standard-state cell if the terminals were connected to a passive circuit. Electrons would flow spontaneously from left to right in the external circuit. 

The purpose of the substrates is to support discrete active components, integrated and passive circuits, capacitors, resistors, varistors, thermistors etc. connected by conducting tracks. The coefficients of expansion of the different materials must be as close as possible in order to avoid the appearance of stresses of thermal origin, susceptible to induce failure of the circuit. Roughness is also an important parameter. It therefore appears that the choice of a material for making a substrate must take into account not only electronic requirements, but also mechanical, thermal and even chemical requirements. 

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