Showing papers on "RC circuit published in 1967"

Microwave circuit characteristics of bulk GaAs oscillators

Abstract: The microwave circuit characteristics of bulk GaAs transit-time mode and limited space-charge accumulation (LSA) mode oscillators have been evaluated experimentally and theoretically. Experimental measurements were performed with a waveguide-coaxial microwave circuit having two experimental degrees of freedom in which the circuit radiation impedance at the device contacts was evaluated by a dyadic Green's function method. Experiments conducted in three rectangular waveguide circuits at fixed bias voltage have established that the LSA mode frequency tuning range is determined by the magnitude and variation of the circuit series inductive reactance X L relative to the device low-field resistance R 0 . At a bias voltage which is twice threshold the tuning range is given by 1/2.4\leq X_{L}/R_{0}\leq 2.4 . No fixed, linear equivalent circuit characterizes the LSA mode. Analysis and experimental results indicate that the device impedance of small-signal transit-time mode oscillators changes from a passive parallel RC impedance well below threshold to an impedance just above threshold which can be approximated by a series RLC circuit. The series L and C decrease linearly with transit-time mode harmonic order number.

Theory of Nonuniform RC Lines, Part II: Analytic Properties in the Time Domain

Abstract: The time-domain behavior of the general nonuniform RC transmission line is presented. It is shown that the impulse response is a "totally positive" density function. The necessary and sufficient condition on a time function to be the impulse response of a nonuniform RC line is obtained. The general properties, including the bounds on the impulse response and its asymptotic behavior, are given.

Active RC Filter Building Blocks Using Frequency Emphasizing Networks

Abstract: The development of economic hybrid integrated filter building blocks is reported on. The units are versatile and can be utilized for a wide variety of applications. They are based on a metliod of network synthesis that generates general second-order networks by pole-zero cancellation of passive RC and active all-purpose frequency emphasizing networks.

Sensitivity of 2nd-order Sallen-key-type active RC filters

Abstract: The sensitivity, to μ−1 (where μ is the open-loop amplifier gain), of the Q factor of a 2nd-order Sallen-Key circuit can be reduced from the conventional value 2Q2/μ to 3Q/μ by increasing the closed-loop gain from 1 to 4/3. However, this increases the sensitivity to passive-element variations. An optimum engineering solution is found by minimising, for given maximum component variations, the resulting variation of Q, rather than the sensitivities. This makes single-amplifier circuits usable for higher Q factors than previously, which is of particular interest for microelectronic realisations of such circuits.

Microwave dryer control circuit

Abstract: 1,232,839. Measuring moisture content. GENERAL ELECTRIC CO. Dec.6, 1968 [Dec.15, 1967], No.58050/68. Heading G1N. [Also in Division F4] The moisture content of fabrics in a tumble drier is determined by measuring their effect on high frequency electromagnetic waves set up in the drum of the drier. As shown in Fig.2, a diode D1 connected to an RC network C2A, R4 detects the standing wave ratio in a microstrip line 40 connecting an antenna 36 to a microstrip line 38 forming the tuned circuit of a printed circuit transistor oscillator.

Telephone system with added main line subscriber facilities

Abstract: 1,195,341. Automatic exchange systems. SUPERIOR CONTINENTAL CORP. 15 Feb., 1968 [2 Aug., 1967], No. 7469/68. Addition to 1,185,678. Heading H4K. [Also in Division H2] The Specification describes two separate improvements in the invention claimed in the parent Application. In one improvement each additional subscriber equipment is adapted to use a conventional A.C. bell ringer while in the other improvement the battery is connected to the line pair so that the direction of the D.C. charging current in the line pair is irrelevant. The parent describes a telephone system in which line pairs leading to ordinary subscriber sets may be additionally used by added subscriber sets employing a carrier frequency and driven by local batteries charged from the exchange. The added sets employ D.C. bell ringers switched on by a transistor circuit on the reception of a carrier frequency. In one improvement (Fig. 5) this transistor circuit 234 switches on an oscillator 418 which generates an alternating (20-oycle) ringing voltage suitable for a conventional A.C. ringer. The oscillator is switched on by a positive potential on a line 236. The potential is divided by a resistor 430 and a diode 428, and biases both of a pair of transistors 424 and 426 towards conduction. One transistor commences to conduct first inducing a current in one half of a centre-tapped primary winding 420 of a saturable transformer. While the transformer is saturating currents induced in each half of a further centre-tapped winding 422 control the bases of the transistors to turn the conducting transistor hard on and switch the other off. When the transformer saturates the current in the winding 420 reduces and the currents in the winding 422 reverse causing the conducting transistor to switch off and vice versa. This periodic reversal (at a frequency determined by the magnetic time constants of the transformer) induce the required alternating current in the secondary winding 440 leading to an A.C. ringer 238a. In one form of the other improvement the battery is connected to the line pair via a full-wave rectifier with a by-pass capacitor for carrier frequency across each end. In another form (Fig. 3) a full-wave rectifier 355 and a carrier frequency by-pass capacitor 392 are connected to the line pair 112 and the output of the rectifier enables a modified Hartley oscillator comprising a transistor 360, an LC circuit comprising a first portion of a primary winding 364 of a transformer 362, and a feedback path comprising the remainder of this winding and an RC network 374, 376. The output of the oscillator as picked up in the secondary winding of the transformer, is again full wave rectified by diodes 380, 382 and a capacitor 386 to give the charging current.

A network transformation for active RC networks

Abstract: A generalization of the well-known RC-CR transformation, which is applicable to active RC networks, is described.

Unijunction transistor artificial neuron

Abstract: A circuit capable of large ranges of pulse rates and pulse widths and comprising a unijunction transistor having one base connected to a d-c source and the other base connected to ground through a resistor. An RC circuit consists of a second resistor and a capacitor connected between the d-c source and ground to determine pulse rate. A diode connects the junction between the second resistor and the capacitor to the emitter electrode to provide a discharge path for the capacitor through the transistor and the first resistor to ground to determine pulse width. A third resistor connects the d-c source to the emitter to bias the transistor to near its firing threshold. Input signal means supply an input signal to said junction to vary pulse rate.

RC-active filters using unity-gain amplifiers

Abstract: A new active-filter configuration consisting of RC elements and a single unity-gain amplifier is suggested. The method may realise many useful 2nd-order transfer functions with a small number of RC elements.

The application of a positive immittance inverter to the design of integrated selective filters

Abstract: One approach to the design of highly selective active RC filters is based on the use of positive immittance inverters (PII), of which the gyrator is a common example. A PII is described which is more general than the gyrator and leads to the design of integrable, highly selective filters.

Comparator for calibration of inductive voltage dividers

Abstract: A guarded comparator for the calibration of inductive voltage dividers against a calibrated standard is described. It features the use of a fixed RC network for phase compensations and a minimum of specialized equipment. Accuracy degradation in voltage-ratio determinations is less than ±0.05 parts per million at, typically, 1 kHz.

A Practical Tantalum Thin-Film Single-Sideband Demodulator Using RC Time-Varying and Active Networks

Abstract: The thin-film circuit described in this paper is equivalent to a demodulator circuit containing an extremely selective filter ("sideband" filter). Such a filter would, in conventional form, require very high Q inductors or, as the Q requirement increases, the use of crystal or mechanical filters. At the frequency of operation of this circuit (1 MHz), demodulation with conventional filters would have to be accomplished in two or more stages so that the selectivity requirement can be decreased for each filter. Thin-film techniques restrict us to circuits using only resistors (R), capacitors (C), and added semiconductor devices (thin-film inductors are not considered here since their inductance values are too small). The current trend is to realize frequency selective networks (conventionally in LC form) as active RC networks. However, although the circuit described here incorporates such a network, the main selectivity requirement cannot be met by present-day active network techniques. The solution is found in the use of time-varying RC networks, i.e., by combining passive RC thin-film phase-shift networks with miniature transistors, used as electronic switches, in the form of so-called quadrature modulation circuits. The phase-shift networks, which in principle can be passive thin-film RC circuits, are in practice more easily realized as combinations of much simpler RC circuits with buffer amplifiers.

A completely tunable active filter using fixed RC elements

Abstract: An arbitrary open-circuit voltage transfer function whose poles and zeros may be independently controlled is realized using RC elements and at most (2n + 2) operational amplifiers, with adjustable gains, where n is the higher of the degrees of the numerator and denominator polynomials of the transfer function.

Optimal design of distributed parameter systems.

Abstract: Optimal design of RC lines distributed parameter systems using gradient technique and variational calculus

Active Filters Operating below 1 Hz

Abstract: Second-order RC filters are synthesized using two voltage amplifiers with gains A1 and A2 As the natural frequency depends on A1 only, and the damping factor depends on A1 and A2, these factors can be chosen consecutively by varying the two gains The passive components need not have variable or accurate values This feature is particularly useful in the realization of filters operating below 1 Hz, and cutoff frequencies down to at least 10-3 Hz can be obtained by exploiting the high input resistance of MOS transistors

A Distributed RC Network Broadband FM Discriminator in Thin-Film Technique

Abstract: The paper describes a frequency discriminator using two distributed RC null networks with different null frequencies, which can be realized in thin- or thick-film technology. The null networks with their null frequencies situated on either side of the carrier frequency use a common input. Their output signals are rectified and subtracted. The demodulated output signal is available either balanced or unbalanced. The analysis covers exponentially tapered and uniformly distributed networks, their difference in sensitivity, and harmonic disitortion due to nonlinearity of the response. The circuit can handle wide frequency deviations of up to /spl plusmn/ 20 percent and delivers an unbalanced output signal of approximately 0.46 volt rms using exponentially tapered networks and an input signal of 1 volt rms with /spl plusmn/ 10 percent frequency deviation. The harmonic distortion in this case is 3.3 percent. Calculated results are compared with measurements of an experimental 1O-MHz discriminator.

Integrated circuit operational amplifier replaces audio transformer in zero to 360° phase shifter

Abstract: A zero to 360° phase shift network having less than 1 percent change in amplitude with respect to phase and using two center tapped transformers with RC circuits and amplifiers is described. The same phase shift is realized using integrated circuit operational amplifiers to replace the audio transformers, thus reducing the size and weight.

Worst-Case Gain Sensitivity with Zero Phase Sensitivity in Active RC Network Synthesis

Abstract: The change in only the magnitude of a network function or the pole vectors due to an infinitely small change in the control parameter K has been usually considered in studying the sensitivity of an active network. In this paper, K is assumed to increase or decrease from its nominal value by finite amounts. A worst-case synthesis procedure, based on a new polynomial decomposition, is presented for designing an active RC network, such that the maximum and minimum modulus of the gain function at a prescribed frequency lies within specified limits and also the phase remains unchanged. An example of a transistor amplifier is worked out, including experimental results.

High-frequency control circuit

Abstract: High-frequency control circuit operating gaseous discharge lamps from an alternating current source includes an alternating current wave-chopping circuit comprising parallel connected oppositely poled controlled rectifiers actuated by a voltage sensitive switch connected to an RC charging circuit, and a commutating branch connected across the controlled rectifiers comprising a capacitor and an inductor in series.

Active distributed RC network

Abstract: A new type of active microelectronic network is introduced, based on the simultaneous application of field effect and signal propagation in a passive distributed RC structure. The analysis of the admittance matrix is carried out, and the location of the dominant poles and zeros is discussed.