Resistance-capacitance Network Research Articles

On the Design of Parallel-T Resistance Capacitance Networks for Maximum Selectivity

A simple analysis is presented for obtaining an expression for the transfer function and hence the selectivity, QT, of a general parallel-T resistance capacitance network. The maximum value of QT obtainable by a suitable choice of elements is shown to be ½. A design procedure for approaching this maximum value is given.An expression has been given for estimating the departure from linearity of the amplitude response characteristic at a particular frequency. This is used to find an optimum value of QT for best performance of the network as an F.M. discriminator at low frequencies. It is shown that the required value of QT is very near its maximum value.An expression for the selectivity, QA, of an amplifier using a general parallel-T resistance capacitance network in the negative feedback line has been deduced and the advantages of having an increased QT explained.

Potential changes produced by application of current steps in motoneurones.

IN cat spinal motoneurones, when current steps are applied across the membrane through the intracellular micro-electrode, the membrane potential changes in an approximately exponential way, but with a certain deviation. Thus, the soma-dendritic membrane of the motoneurone has been assumed to behave as a resistance and a capacitance in parallel1,2, and the deviation has been attributed to the cable-like property of dendrites, the dominance of which in forming the effective surface area of motoneurones has been emphasized recently3. As will be described, however, the potential produced by current steps in motoneurone membrane shows a considerable overshoot, which has so far been overlooked because the current steps used previously were generally too brief to reveal the later decline of the potential. This electrical behaviour of the membrane suggests that the equivalent electrical circuit of the membrane is not a simple resistance-capacitance network.

Parallel-T Resistance Capacitance Selective Current Amplifier

The problem of selective amplification using parallel-T resistance capacitance network to provide current feedback in current amplifiers has been analysed. The effect of varying the relation between impedances of the series and shunt arms (expressed as a parameter ‘n’) of the parallel-T network is given. The important characteristics of a selective amplifier are peak gain, frequency of peak gain and selectivity. It is shown that these quantities can be obtained from known values of amplifier gain, the parameter ‘n’ and the load resistance. The analysis given in this paper facilitates the determination of the characteristics of a current amplifier with parallel-T feedback network working as a selective voltage or current amplifier between resistive input and output impedances.

Long-period seismographs

ABSTRACT Descriptions and theories of a number of different seismographs developed particularly for recording of very long-period seismic waves are presented. These include (1) electromagnetic strain seismograph with galvanometer of 8 minutes period and photographic recording; (2) displacement transducer strain seismometer with resistance-capacitance network and short-period galvanometer photographic recorder or with ink-writing recorder; (3) electromagnetic pendulum seismometer with RC network having transfer characteristic of a long-period galvanometer recorder or a heated stylus visible writer; (4) electromagnetic pendulum with period increased tenfold or more using shunt capacitance; and (5) electromagnetic pendulum with condenser-lengthened period and triple RC integrating network recording with either heated stylus visible writer, ink writer, or short-period galvanometer photographic recorder.

New Applications of Impedance Networks as Analog Computers for Electronic Space Charge and for Semiconductor Diffusion Problems

Starting from a general partial differential equation of the second order, which includes the equations of Laplace, of Poisson, and those of semiconductor diffusion problems, an equivalent equation with finite differences is discussed. This leads to resistance and to resistance-capacitance networks. Resistance chains are applied to high vacuum diodes of one-dimensional character (plane, circular, and spherical systems). Results are within about a per cent of the exact solutions. Resistance-capacitance chains and networks are applied to semiconductor diffusion problems with space and surface recombination, yielding known and new results pertaining to p-n diodes. A plane resistance network is applied to a triode with electronic space charge and yields the anode current vs grid voltage curve within a few per cents of the published value. These results may lead to considerable savings in the design of new tubes.

Automatic Machine for Testing Capacitors and Resistance-Capacitance Networks

The modern telephone system consists of a variety of electrical components connected as a complex network. Each year, millions of relays, capacitors, resistors, fuses, protectors, and other forms of apparatus are made for use in telephone equipment for the Bell System. Each piece of apparatus must meet its design requirements, if the system is to function properly. This article describes an automatic machine developed by the Western Electric Company for testing paper capacitors and resistance-capacitance networks used in central office switching equipment.

Design of Parallel-T Resistance-Capacitance Networks

This paper deals with parallel-T resistance-capacitance networks which, for a source of finite resistance and a resistance load, have transfer characteristics symmetrical with respect to the resonant frequency. It is shown that there exists a network with the minimum loss for a prescribed frequency discrimination. Formulas are presented for the design of such a network.

Measurement of Minority Carrier Lifetime and Contact Injection Ratio on Transistor Materials

A method of measuring minority carrier lifetime and injection ratios of contacts on transistor materials is described. The lifetime is obtained by observing the decay of resistance of a filament throughout the duration of an injecting pulse. The use of a bridge circuit, incorporating a resistance-capacitance network which is electrically analogous to the filament, enables the lifetime to be read off a calibrated dial. The range of lifetime, which can be measured with the equipment in its present form, extends down to 1 μsec, the accuracy being usually about 5%. The method is also capable of determining minority carrier mobilities. Examples of measurements of lifetime and injection ratio of soldered contacts in n-type germanium are given. The injection ratio is found to rise linearly with the current through the contact

Synthesis of Passive RC Networks with Gains Greater than Unity

This paper illustrates the fact that three-terminal passive resistor-capacitor networks are capable of having unity voltage gain at zero frequency and higher than unity gain over a prescribed frequency band. A general design procedure for synthesizing a transfer function with these properties using, insofar as possible, known methods of synthesis is outlined. Together with suggestions for further work, two examples are presented to illustrate the method.

The Synthesis of Resistor-Capacitor Networks

This paper develops a general method of synthesis of a prescribed ratio of output-to-input voltage in the form of a resistor-capacitor lattice. The method is described for both the cases where the output terminals are unloaded and where a resistor-capacitor load is specified. The methods of transformation of the lattice to unbalanced structure are outlined. Illustrative examples are given for each of the cases discussed in the paper.

An instrument for complete symmetrical-component analysis

Established methods for the resolution of an unbalanced system into positive-and negative-sequence components are extended to give information about their relative phase-displacement. The method developed depends on the inherent property of dynamometer instruments that, for given currents in the coils, the deflection is proportional to the cosine of their phase difference. A dynamometer instrument of ordinary design was modified simply for the purpose by separating the coils and connecting the ends to external terminals, two similar resistance-capacitance networks being added. If it is assumed that the zero-sequence component is absent, or has been eliminated, three readings r1, r2 and r12 and one unrecorded test of a qualitative nature are sufficient for a complete analysis. The test serves to determine the sign of the phase angle, the sequence components r1 and r2 are given directly, and the expression cos ?=r122/(r1r2) enables the phase angle to be found. The only calculation is very simple, and the solution can be obtained quickly from nomogram.

Square-Wave Analysis of Compensated Amplifiers

A complete analysis of a single-stage compensated video-frequency amplifier is presented. In this amplifier high-frequency compensation is obtained by the use of a shunt peaking coil in series with the plate load resistance, and low-frequency compensation is obtained by using a resistance-capacitance network in series with the plate load resistance. Both square-wave and sine-wave input voltages to the amplifier are considered. The square-wave analysis consists of a determination of the output wave shape when a symmetrical square wave is applied to the input. Equations for the output wave shape are derived and put in such a form that the output wave shape may be plotted for any desired frequency of input square wave. Output wave shapes are drawn for a number of typical operating conditions, and the corresponding frequency- and phase-response curves are drawn for comparison. The effect of the cathode impedance, assumed negligible in the square-wave analysis, is considered briefly in a separate section, and its effect on low-frequency compensation is discussed. Derivations of many of the equations used are found in the Appendix.

Note on a Parallel-T Resistance - Capacitance Network

Formulas are developed for the performance of a four-terminal parallel-T resistance-capacitance network which serves for the elimination of a given frequency. It is shown that an unsymmetric form of the network is advantageous when a high degree of frequency discrimination is desired.

Theory and Application of Parallel-T Resistance-Capacitance Frequency-Selective Networks

This paper deals with the theory and application of the parallel-T resistance-capacitance network, and gives a more general treatment of this network than that found in earlier papers. Using wye-delta conversion methods, the parallel-T resistance-capacitance network is represented by a single equivalent pi circuit. By introducing symbols corresponding to frequency and component values, simple expressions are derived for the impedance of the pi arms, as well as the network transmission, at any frequency. Since no arbitrary relationships are assumed between component values, the derived expressions are general. The practical application of the network is also considered. Three versatile circuit embodiments are described, and the effects of deviating from specified component values investigated. A calculation is made to illustrate the application of the network to a negative-feedback circuit using a single stage of voltage amplification.

Extending the Frequency Range of the Phase-Shift Oscillator

Methods for facilitating the design of phase-shift oscillators at extreme frequencies of a fraction of a cycle to a few megacycles are discussed. It is shown that, if the input impedance of each section of a lumped resistance-capacitance network is made K times that of the previous section, the gain required for oscillation can be reduced to a theoretical minimum of 8 for a three-section network with K high, as against 29 for a K of unity. A new circuit element called the "resistance-capacitance transmission line," consisting of a resistance covered by a well-insulated and grounded metal surface, is introduced and is analyzed as a phase-shifting network to give reliable operation in a phase-shift oscillator at frequencies up to a few megacycles. Curves are presented to facilitate the design of the latter type of oscillator. Various configurations of the resistance-capacitance transmission line are discussed and experimental results are presented.