Showing papers on "Amplifier published in 1970"

Optical parametric device

Abstract: An optical parametric device is described which may be used as an amplifier, oscillator, or frequency converter, and which is operable in the infrared or visible spectral regions. The device utilizes a dielectric optical waveguide or tuned cavity, which structure may comprise the depletion layer of a semiconductor junction, the dielectric material of which exhibits nonlinear susceptibility. An intense, appropriately oriented, optical pump induces a non-linear electric polarization in the material of the dielectric structure. Traveling wave or discrete circuit parametric interaction occurs within the structure between the pump and an input signal. Under appropriate conditions, oscillation, amplification, and/or frequency conversion may be obtained.

Pulse Power Failure Modes in Semiconductors

Abstract: Semiconductor devices operating under both biased and unbiased conditions are vulnerable to permanent damage from relatively moderate levels of pulsed electrical energy, particularly of submicrosecond pulse duration. An experimental study was performed to determine the permanent damage levels associated with a number of different devices and to identify the failure mechanisms associated with each. The device types investigated included general purpose and high speed computer diodes, a medium power diode, medium frequency and UHF transistor amplifiers, and a dielectrically isolated diode gate expander. The permanent damage levels associated with these devices were determined both for positive and negative polarity pulses at different conditions of quiescent bias and pulse width. The pulse duration times included the range of 30 to 300 nanoseconds, and in some instances, up to 1 microsecond. Failure models for both thermal second breakdown induced damage to the semiconductor junction and thermal damage to the device interconnecting leads and metallization patterns were also developed.

Application of Volterra series to intermodulation distortion analysis of transistor feedback amplifiers

Abstract: This paper analyzes the intermodulation distortion of a solid-state feedback amplifier. Each transistor of the amplifier has been represented by a frequency-dependent model incorporating four nonlinearities. The Volterra series is used as the analysis tool. The primary motivation for this study is that intermodulation distortion is a critical problem in high-frequency long-haul solidstate systems. A computer program that calculates the amplifier intermodulation distortion has been developed. This program can be used to select the optimum bias point of each stage, optimum interstage and feedback networks, and optimum load and source impedances. Good correlation between calculated and measured results was obtained. The closed-form expressions derived show that the feedback is fully effective in reducing the open-loop second-order distortion and that the feedback may not significantly reduce the open-loop third-order distortion, if the "second-order interaction" phenomenon is dominant. The second-order interaction is explained in detail in this paper.

Four-quadrant multiplier circuit

Abstract: A wideband differential amplifier comprises a pair of differentially connected control devices, for example transistors, having a pair of semiconductor junction input devices coupled thereto for receiving complementary input currents. The input devices exhibit logarithmic characteristics substantially compensating for nonlinear properties of the pair of differentially connected control devices, whereby a linear rather than a nonlinear amplifier current output is produced. Multipliers, cascaded amplifiers, and other useful circuit configurations are provided.

Nonlinear Phase Shift in Traveling-Wave Tubes as Applied to Multiple Access Communications Satellites

Abstract: A modern communications satellite typically amplifies many frequency-modulated radio-frequency carriers in a single common amplifier. The nonlinear phase versus input power behavior of traveling-wave tubes (TWT) and its impact on intermodulation noise and intelligible crosstalk is treated. A theoretical model is presented, which allows calculation of the multicarrier performance of the TWT, and an experimental verification of the model is given.

The decibel relationships between amplifier distortion products

Abstract: Assuming that the transfer characteristic of the amplifier can be represented by a power series with three terms, an analysis is carried out to determine the frequency and amplitude of each distortion component. To make it easy to apply these results to a practical situation, the necessary constants are defined to enable expressing these relationships in decibel terms. The results are simple expressions which involve adding or subtracting decibel constants from products of the output levels, in dBmV, by integers. Cross modulation, compression, and differential gain are treated, as well as the various harmonics and beats. The usefulness of these results in practice is discussed, as well as the extent of agreement which can be expected between theory and practice.

Negative-resistance diode power amplification

Abstract: An analysis is presented for the nonlinear behavior of power amplifiers utilizing negative-resistance diodes in a reflection circuit. The analysis applies to both stable and locked-oscillator modes of operation. Special emphasis is given to a simple model involving a cubic nonlinearity in the I-V relationship, and to the idealized LSA device in an amplification mode.

Dark current correction circuit for photosensing devices

Abstract: In a flicker-type photosensing device, photosensor dark current is corrected for by applying the output of the photosensor to a current-to-voltage mode amplifier including a special dark current correction loop. In particular, the amplifier has connected between its input and output terminals a loop including a resistor, a grounded capacitor, a gating arrangement adapted to close the loop only during those periods when no light beam is applied to the photosensor, and a second resistor for limiting the capacitor charging rate. In operation, the capacitor charges while the gate is closed during the dark period; and, during pulse periods when the gate is open, it discharges to reduce the photosensor current by an amount nearly equal to the dark current.

Nonideal performance of two-amplifier positive-impedance converters

Abstract: Positive-impedance converting networks may be used to realize driving-point inductance and frequency-dependent negative resistance. The Q factors of these immittances are evaluated over a wide frequency range in terms of the relevant parameters. Three distinct types of Q- factor behavior are derived and it is shown that extended wide-band operation may be achieved such that Q factor is virtually independent of amplifier phase shift. The use of design-value asymptotes is explained as a means of determining the behavior of practical circuits.

Electrically isolated signal path means for a physiological monitor

Abstract: A circuit for providing electrical isolation between a patient and physiological monitoring apparatus comprising an amplifier, having applied to the input thereof a physiological signal from the patient, and a first circuit branch including an isolation transformer connected between a modulator and a demodulator for connecting a d.c. voltage source of relatively low magnitude to the amplifier. Connected to the amplifier output is a second circuit branch comprising an isolation transformer connected between a modulator and a demodulator, and the output of the demodulator is coupled to the input of physiological monitoring apparatus. Each of the isolation transformers includes an extremely low capacitance between the primary and secondary windings thereof to present an extremely high reactance to low frequency, including line frequency, alternating current and each is capable of withstanding relatively high voltages without breakdown.

Intermodulation Effects in Limiter Amplifier Repeaters

Abstract: A method is presented for analyzing intermodulation (IM) spectra in limiting amplifiers using a statistical approach Engineering approximations are derived for the case of a large number of input signals The accuracy appears to be good down to seven signals The approach permits analysis of arbitrary locations (in frequency) of the input signals Possible ways of reducing IM interference in limiting satellite repeaters are discussed The analysis is generally restricted to the ideal hard-limiting amplifier however, its applicability to other nonlinear characteristics is illustrated Additional sources of degradation, such as amplitudemodulation-frequency-modulation (AM-FM) conversion and system phase nonlinearity, are not treated

High-speed gallium-arsenide Schottky-barrier field-effect transistors

Abstract: The letter shows that gallium arsenide is a well suited material for high-frequency field-effect transistors. From preliminary measurements on realised transistors, it is shown that the frequency limit for power amplification is considerably higher than for other known transistors. The processes involved are briefly described.

Anticorrelation in Two-Photon Attenuated Laser Beam

Abstract: The density matrix in the $P$ representation of a beam of radiation amplified by a two-photon amplifier has been derived up to the lowest order in the time-dependent perturbation theory without placing any restriction on the population of the state of the atom. It is shown that a laser beam containing noise in addition to the harmonic signal exhibits anticorrelation after being passed through such an amplifier, if less than one-sixth of the total number of atoms are maintained in the excited state.

Pulse-Area-Pulse-Energy Description of a Traveling-Wave Laser Amplifier

Abstract: The effects of a transverse mode, degeneracy, overlapping transitions, background losses, and transverse population variations are included in an analysis of light-pulse amplification in a system with an inhomogeneously broadened gain profile. Over a wide range of resonant gain and background loss, the steady-state pulse energy is proportional to the inverse cube of the pulse width, in accord with the observations of Frova et al.

Electrosurgery unit and instrument

Abstract: An electrosurgery unit for carrying out various medical or dental operations. An oscillator of the unit provides an output signal of a given high frequency, and this signal is received by a pre-amplifier which provides an amplified signal. An output amplifier receives the latter signal and provides a given output, while an output coupler connects the output of the output amplifier to a high-impedence load which in the case of dental surgery may be the gums which are treated. A power supply is provided for supplying voltage to the oscillator, pre-amplifier and output amplifier. For coagulating operations the unit provides a fully modulated high frequency signal. For cutting operations, the unit provides a ripple-free constant amplitude high frequency output. A selecting switch is provided for selecting between the operations.

Housing for electrical equipment

Abstract: An electrical housing particularly but not exclusively for cable television amplifier units. The housing has a base and a lid which are hinged together by one or usually more pairs of hinge elements. One of each pair being releasably received in a socket on the lid and the other being releasably secured in a socket on the base, the two elements being joined by a hinge pin. The lid can be removed and replaced by releasing it from its associated hinge element and securing a new lid (which may be substantially similar to the base) to that element.

Circuits for driving loads such as liquid crystal displays

Abstract: A pair of amplifiers and a load such as a liquid crystal connected between the output electrodes of the amplifiers. In response to one relationship between the input signals to the amplifiers, an alternating turn-on voltage is applied via at least one of the amplifiers to the liquid crystal for causing it to scatter light. In response to another relationship between said input signals, the light scattering produced by the liquid crystal is reduced to a relatively low value.

Miniature tv antenna

Abstract: An antenna for TV reception predominantly in the low band and high band VHF ranges having dipoles of significantly reduced physical length as compared with conventional dipoles for reception of signals respectively in the low and high band VHF ranges. Inductive elements are employed to form a portion of the dipole length to permit significant reduction in the physical length of the dipole. The dipoles are electrically isolated from one another by suitable trap circuits to isolate high band VHF operation from low band VHF operation. Lossy components are deliberately added to the dipole section of the antenna to provide significantly improved noise matching and power transfer between antenna and amplifier. The inductive elements further provide good impedance matching between antenna and amplifier to optimize power transfer. The antenna is provided with end loads of the capacitive-type for improving both current magnitude and current distribution across the dipole in both low band and high band VHF operation. Separate amplifier channels are provided for low band and high band VHF signals to improve gain and reduce intermodulation and cross modulation effects, among other. A passive UHF section may be integrated into the array.

Direct gain measurements of an organic dye amplifier

Abstract: Amplifier gain measurements were made on the dye rhodamine 6G in ethanol. Gain was measured as a function of wavelength and time for a 1 × 10−4 M solution. The peak gain coefficient was measured to be 95 dB/m at a pump energy of 21.5 J. This same pump energy produced 55 mJ of laser output from a 3.8‐cm‐long cell in a mode diameter of 3.6 mm.

Corrective circuit for an active narrow notch filter

Abstract: An active narrow notch filter is adapted for connection between a power source and a load to filter out noise signals appearing on the power lines. A feedback loop having a stop-band notch filter is connected to the power lines and feeds interference signals to an amplifier which drives a correction transformer inserted in the power lines to cancel out interference signals from the power source. A corrective circuit is connected to form a feedback loop with the amplifier and notch filter to generate a feedback signal that is applied to eliminate any power line signal that passes through the notch filter. This corrective circuit has a first detector circuit producing an error signal which is fed through a first modulator to generate one component of the feedback signal that cancels out power line signals passing through the notch filter, and a second detector circuit and modulator that produces a second component of the desired feedback signal that is in quadrature with the first component.

Analog signal to discrete time interval converter (asdtic)

Abstract: An electronic signal conversion device is disclosed. The concept of pulse modulation includes in the sense of this invention the process of sampling a source of electric energy by one or several switches, and the electronic function that controls this switch or switches; any utilization of averaging devices to smooth the ensuing pulses such as filters are excluded as part of this process, except that a filter may be inserted ahead of a lead to be energized. The device is particularly useful wherever conversion of analog signals to discrete time signal intervals for purpose of pulse modulation is required. However, the invention has general utility and is presently being used with specific power supplies in the space program and communication technology. In addition, the device lends itself to incorporate a reference source and feedback network as used with power amplifiers and direct current pulse modulated power converters. The device maintains its accuracy of expected operation notwithstanding variations in its component characteristics, variations of applied voltage waveforms and supply voltages.

Portable gas leak detector

Abstract: In a portable gas leak detector for determining the location of leaks of gases having a different thermal conductivity than the ambient surroundings and having a conductivity detector, first amplifier and output, the improvement of a positive and a negative drive amplifier connected to the first amplifier with separate indicating lights connected to each of the positive and negative drive amplifiers for indicating the relative conductivity of the sample to the ambient surroundings and whether the detector is approaching or leaving a leak. A feedback loop connected across the first amplifier which includes an amplifier having a memory retaining means for zeroing the output for overcoming temperature induced drift in the detector and nulling the output of the detector thereby allowing accurate pinpointing of the leak. Means for actuating the feedback loop including a manual switch, an automatic switch when the output is less than a predetermined amount, and an automatic switching means when the output is more than a predetermined amount for a certain period of time.

Three-amplifier gyrator

Abstract: Three identical inverting amplifiers are connected in a circuit combination of two amplifiers in cascade across the remaining amplifier. The circuit configuration, accomplishes wide banding in a gyrator.

Wide-Band Reflection-Type Transferred Electron Amplifiers

Abstract: Stable CW and pulsed linear-reflection-type amplification at C- and X-band frequencies using epitaxial-GaAs transferred electron devices is described. These devices have a doping density-length product (nl) greater than 5 x 10/sup 11/cm/sup -2/. Criteria for avoiding the normal instabilities are discussed with specific regard for the circuit impedance, operating bias-voltage material characteristics, and the device temperature. The active impedance of a stable device has been measured, along with the effects of the package parasitic. These data were utilized to design multiple-tuned wide-band circulator-coupled coaxial-amplifier networks. Instantaneous CW bandwidths of nearly 1 octave have been measured in C-band, and instantaneous bandwidths of 4 GHz have been measured in X-band with single-stage Iinear gains from 6 to 12 dB. A -1-dB gain compression power output of 250 mW, with a saturated power output approaching 1 watt, has been realized from a single device. The noise figure of a single-stage amplifier has been found to be 15 dB. The phase response of a typical amplifier has been found to be linear with a differential phase shift of less than 20/spl deg/ /GHz. The amplitude linearity has been related to third-order intermodulation distortion and found to be comparable to that obtainable from traveling-wave-tube amplifiers (TWTAs). In a two-stage configuration a small-signal gain of 22 dB and a fractional bandwidth of 35 percent have been realized in C-band. A novel scheme for studying the gain response of pulse-biased devices using swept-frequency techniques has been developed. Pulsed amplification has been obtained with a power output of 2 watts at a 5-percent duty cycle with a conversion efficiency of 6 percent and a bandwidth of 1 GHz.

Overload Recovery Circuit for Charge Amplifiers

Abstract: In this paper the operation of low noise charge preamplifiers under high instantaneous pulse rates - "bursts" - is considered. An overload recovery circuit employing a field-effect transistor as the switch for the recovery current is described. The overload charge generated in the detector by the radiation burst in a time short compared to the small signal resolving time of the spectrometer may be 105 or more times larger than the charge due to a single particle to be measured between the bursts. The recovery time of the charge amplifier with the recovery circuit is less than 10 ?sec. With a conventional amplifier-filter, the recovery time of the system to within the noise level is 50 to 100 ?sec. The increase in noise due to the recovery circuit corresponds to an increase in the input capacitance of the charge amplifier of 2 pF.

Signal transmission system employing electroacoustic filter

Abstract: An acoustic-surface-wave system is used in coupling a signal source to a load. This system comprises an acoustic wave propagating medium with a single transducer at one end and at least a pair of transducers at the other. One end constitutes the input which connects to a signal source and the other connects to a load. A matrix including a pair of variable gain amplifiers couples the pair of transducers to its assigned terminal apparatus and controls the relative amplitudes of the signals transmitted by this transducer pair in determining the amplitudefrequency response of the system. Further control of the response characteristic is available by using unequal spacing along the medium of the members of the transducer pair relative to the aforesaid single transducer. The acoustic-surface-wave system is also used in a unique frequency-modulation detector and also in neutralizing feedback in transistor amplifiers.

Travelling-wave amplifier using thin epitaxial GaAs layer

Abstract: A solid-state travelling-wave amplifier has been fabricated in 1 µm n type epitaxial GaAs on a semi-insulating substrate. It shows a net gain around 5, 7.5, 9 and 11.5 GHz, with a maximum value of 13 dB at 11.5 GHz. Other features include c.w. operation, 20-30 dB isolation, and voltage-controlled phase shifting with constant gain.

Centrifuge with sludge level sensing means

Abstract: The centrifugal rotor has a sludge-accumulating space from which an indicating channel extends inwardly to the region of the rotor axis. Clogging of the outer end of this channel by sludge is sensed by a device comprising a pressure signal amplifier, a pressure differential gage, a pressure-transmitting connection between one side of the amplifier and one side of the gage, a connection for transmitting a pressure of the liquid being separated, and a connection for transmitting a pressure of the liquid in the indicating channel, one of said last two connections leading to the other side of the amplifier and the other of said last two connections leading to the other side of said gage. Thus, the arrangement provides a measure of the difference between the pressure of the indicating liquid and the pressure of the separated liquid.

Lamp outage indicator

Abstract: A monitoring circuit wherein a change in the electrical load in an automobile lamp circuit causes the output of a sensing amplifier to increase and actuate a control switch that lights an indicator to show the change in load.

Rf system for measuring the level of materials

Abstract: In an RF system which measures the level of materials, the probe includes a measuring electrode and a guard shield. The guard shield is interposed between the electrode and a conductive member, commonly the container for the material, throughout the body of the probe. The variable capacitance between the measuring electrode and the conductive member is a measurement of the level of the material. This variable capacitance is connected in a capacitance bridge. An operational amplifier has its input connected to the junction of two fixed adjacent arms of the bridge and has its output connected to the guard shield to maintain the guard shield at the same potential as the measuring electrode. This prevents deposits of foreign material on the probe from affecting the measurement. An output amplifier is connected between the output of the first amplifier and a junction of two opposite adjacent arms of the bridge. Connection of the output amplifier in this manner prevents changes in the input impedance of the output amplifier from changing the zero point of the bridge.