Showing papers on "Amplifier published in 1968"

A new wide-band amplifier technique

Abstract: Precision dc-coupled amplifiers having risetimes of less than a nanosecond have recently been fabricated using the monolithic planar process The design is based on a simple technique that has a broad range of applications and is characterized by a stage-gain- bandwidth product essentially equal to that of the transistors, and a very linear transfer characteristic, free from temperature dependence

Power converter circuits having a high frequency link

Abstract: 1,261,838. Static converters. GENERAL ELECTRIC CO. 9 April, 1969 [16 April, 1968], No. 18197/69. Addition to 1,261,392. Heading H2F. [Also in Division G3] In a power converter as claimed in parent Specification having a control circuit for selectively rendering conductive the solid state switching means in primary and secondary current paths at a switching rate frequency which is high compared with the supply frequency, there is further provided a phase shift circuit coupled to the control circuit to render conductive the primary and secondary current paths at a selected phase angle one with respect to the other, whereby to control the output voltage. The switches may be transistors as shown, Fig. 3, or Gate-turn-off thyristors (Fig. 10, not shown). Converter circuit, Fig. 3.-As in the parent Specification the load voltage e 2 is at the same low. frequency as the input side voltage e 1 , the input current being chopped by transistor switches and applied in opposite directions alternately through a ferrite core transformer 14 at a high frequency switching rate, e.g. 5-10 kHz. The h.f. current at the secondary side is reformed into a low frequency waveform by the secondary side transistor switches also operating at the h.f. rate. Reversibility of power flow through the converter is possible. Each switch means is bidirectional and as shown, Fig. 3, comprises an anti-parallel pair of' transistors Q1-Q2, Q3-Q4, Q5-Q6, Q7-Q8 respectively. Both transistors in a pair preferably receive base current from a control circuit 52 simultaneously and the circuit conditions determine which conducts or alternatively the base signals may be applied via logic circuits. Thus during the positive half cycles of low frequency input, Q2 conducts via diode 29 and in negative half cycles thereof, Q1 conducts via diode 28 and the transformer primary. In normal operation (i.e. 0 degree phase shift between input and output side switches) Q1, Q2 receive base signals at the same time as Q5, Q6 the transistors Q3, Q4, Q7 and Q8 being OFF. During the next h.f. half-cycles Q3, Q4, Q7, Q8 receive base signals and the others are OFF, and so on. D.C. supply.-The connection of the converter to a D.C. source is envisaged wherein the phase shift control is modulated to obtain a desired output waveform to a load. To obtain a sine wave the phase shift is changed between 0 and 180 degrees and then between 180 and 0 degrees according to a sine wave function. Alternatively the output may be D.C. Control circuit, Fig. 9.-An oscillator 58 supplies clock pulses at twice the h.f. switching rate to drive a flip-flop 59 connected to an amplifier 61 which provides base signals for the input side transistors Q1 to Q4. The oscillator pulses are also fed to a phase shifter 62 which actuates a second flip-flop 63 connected to a base signal drive amplifier 64 for the output side transistors. The output drive 63 is thus synchronized with the input drive 59 but is appropriately phase delayed by the shifter 62. Voltage regulation.-The output voltage is sensed by a transformer 48, is rectified and compared in a differential amplifier 68 with a pre-set level VR eg and fed to the phase shifter 62 which causes the output side transistor to change conduction states at a different time from the input side transistors, in either leading or lagging sense. Fig. 4 (not shown) illustrates the output voltage and transformer voltage waveforms for different degrees of phase difference between input and output transistor switches. For 90 degrees phase difference for instance the output voltage is zero. Current regulation.-Load current is sensed by a C.T. 49 and compared with a desired value IR eg in a circuit 71 and a difference value output operates the phase shifter 62 to adjust the output voltage and hence load current. Alternatively the load current signal is compared with a desired current limit value I Lim in circuit 71, the phase shifter operating to reduce the output voltage and current, overriding the voltage regulator. Overcurrent protection.-If overcurrent sensed persists for a time determined by a timer 73 (e.g. 20 low frequency input cycles) a base signal modifying circuit 74 sends a signal to drive amplifiers 61, 64 to cut off base signals to all the transistor switches, or to the input side transistors only, preferably at load current zero to minimize reactive current. Alternatively, circuit. 71 may operate the phase shifter 62 if excess current persists for a pre-set time, to give a full phase shift of 90 degrees between input and output side switching causing zero output voltage. After a time delay to allow reactive current to die all the transistors are turned OFF.

Flicker Noise of Phase in RF Amplifiers and Frequency Multipliers: Characterization, Cause, and Cure

Abstract: The high phase stability of atomic frequency standards has called for the development of associated electronic equipment of equivalent or superior stability. We have surveyed the performance of existing high quality frequency multipliers and R F amplifiers which operate in the range of 5 MHz to microwave frequencies. We were most interested in the phase noise in the range of Fourier frequencies, f , of about Hz to l o t 3 Hz, since most electronic servo systems in existing atomic frequency standards use modulation frequencies which fall within this range. This range also includes the passive linewidths of existing atomic frequency standards.

Enhancement of optical receiver sensitivities by amplification of the carrier

Abstract: The amplification before detection of the carrier of a modulated optical signal by a narrow-band quantum amplifier enhances the signal-to-noise ratio, particularly when the signal wave-front is distorted. A further improvement is obtained by using a combination of wide-band and narrow-band quantum amplifiers. The practical application of these schemes requires a degenerate regenerative ring-type amplifier capable of amplifying arbitrary transverse field configurations. Experiments show that such an amplifier with a gain of 24 dB and a bandwidth of 1 MHz is feasible. The incident beam axis can be displaced by as much as ten times the beam-waist radius without losing more than 4 dB in gain. Frequency modulation may be converted into amplitude modulation by the phase shift introduced in the carrier.

Apparatus using smith-purcell effect for frequency modulation and beam deflection

Abstract: An electron beam is deflected across the surface of a metallic grating to generate Smith-Purcell radiation. An amplifier which receives generated radiation from the grating from a predetermined direction will produce a frequency-modulated light or microwave beam. An amplifier which receives a signal of predetermined frequency and amplifies the signal at the angular position from which received serves as a beam deflector.

Hybrid integrated lumped-element microwave amplifiers

Abstract: This paper describes the development of microwave lumped-element thin-film amplifiers. The basic design philosophy underlying lumped inductors and capacitors at microwave frequencies is reviewed, showing how Q's of 100 are achieved. A variety of tunable input, output, and interstage integrated lumped-element networks for transistor amplifiers were fabricated. The gain and efficiency of 2-GHz class-C operated transistors mounted in these circuits were comparable with the best performance achieved by the same transistors in less lossy coaxial circuits. The measured losses (1.2 dB) at 2 GHz were very close to those calculated using the design parameters. Single-stage amplifiers at 2 GHz achieved one watt of output power with 4 dB of gain. At somewhat lower power levels more than 6 dB of gain was achieved. The circuits allowed the operation of low-power level class-A amplifiers with over 13 dB of gain. Cascaded operation yielded more than 17 dB of gain with 0.8 watts of CW power. It is concluded that lumped elements can be fabricated by thin-film technology and will play an important role in microwave integrated circuits.

IF Amplifier using C/SUB c/ compensated transistors

Abstract: An integrated bridge network of four transistors is used as a self-neutralized active element in tuned RLC amplifier designs. The bridge network compensates for the transistor collector-base junction capacitance (C/SUB c/), yielding a 95-percent reduction in the common-emitter reverse transmission admittance. IF amplifier stages that achieve the maximum unilateral power gain of a common-emitter transistor while maintaining excellent alignability are realized using the C/SUB c/ compensated transistor structure. Variations of the relative bias current levels of the transistors in the bridge network provides gain control by way of signal cancellation. This technique produces minimal frequency response variations of the amplifier stage being controlled. A noise analysis shows output signal to noise ratio at maximum attenuation can be a performance limitation.

RC-Amplifier Resonators for Active Filters

Abstract: Active filters may consist of a cascade of isolated resonators, with each resonator supplying a single pair of complexconjugate poles. This paper supplies a detailed analysis of some RC -amplifier resonators whose characteristics are well suited for practical filters. The calculations are facilitated by a set of sensitivity identities. One resonator, taken from the Sallen and Key catalog, is shown to have extremely low passive sensitivities: S_{Z}^{Q} = \pm \frac{1}{6} for all passive elements. Active Q multiplication is used to extend the usefulness of the circuit. Analysis of the dualintegrator feedback resonator shows that it is notably insensitive to amplifier parasitics. Finally, the dual-integrator concept is realized in a resonator that uses only two amplifiers. The several resonators supply a range of useful pole- Q 's from low values to several hundred.

Electronically tuned antenna system

Abstract: 1,199,136. Aerial coupling arrangements. MOTOROLA Inc. 19 March, 1969 [16 April 1968], No. 14460/69. Heading H4A. A receiving aerial 10, Fig. 1, such as a rodtype motor-car aerial, is remote from associated signal processing stages and has a tank circuit located at its base which includes a voltage variable tuning reactance 26. As described, the tank circuit is contained in a housing 12 and comprises a transformer 18 with a primary winding 20 and a secondary winding 22. The voltage variable reactance 26 is a two-terminal PN junction semi-conductor capacitor device, and it is connected with a blocking capacitor 24 across the winding 22. Signals from the aerial 10 are coupled to the signal processing stages by a coaxial cable 28, which also connects variable biasing voltage from a tuning potentiometer 50 to the element 26 via resistors 52, 54. Output from the potentiometer 50 is also used to tune a heterodyning oscillator 32. In another embodiment (Fig. 3, not shown) a transistor-type R.F. amplifier is located with the tank circuit at the base of the aerial. Three leads are provided to the signal processing stages, one for output from the R.F. amplifier, one for A.G.C. of the R.F. amplifier, and one for bias voltage for the voltage variable capacitor in the aerial tank circuit.

New technique for combining solid-state sources

Abstract: The advent of many new moderate power solid-state devices has created a renewed interest in the techniques for combining these devices to achieve even higher powers. This paper describes a new technique for combining large numbers of energy sources by using a dense array of radiating elements. The impedance of the radiating elements, as determined theoretically and confirmed using an array simulator, may be well mat to parallel one hundred transistor amplifiers has a net gain of 4.75 dB at 410 MHz with 100-watts output. Tests in which individual failures were simulated indicate that array elements were well isolated from each other.

GaAs laser amplifiers

Abstract: Experimental results are presented on the operational characteristics of GaAs laser amplifiers very closely coupled to a laser oscillator. The separation between the oscillator and the amplifier was varied from 0.2 to 2.0 microns. The amplifiers were made by lapping one end at an angle of 10 to 15 degrees. This angle is several times larger than the critical angle for confinement of radiation in GaAs lasers that is estimated from experimental data to be between 2 and 3 degrees. The measured signal gain is a decaying function of input power and approaches a value of 2 to 4 for large input signals. A maximum amplifier gain of about 150 was obtained for an input signal of 2 mW/mil junction width (corresponding to an optical flux-density of about 8 kW/cm2incident on the input side of the amplifier). At this input power level, the output fluoresence is reduced by about 50 percent and the internal oscillatory modes of the amplifier are almost completely quenched. The ratio of the oscillator output actually coupled into the amplifier to the measured output from the oscillator was estimated from gain saturation measurements. It was found to be inversely proportional to the cleaved separation between the oscillator and the amplifier and was estimated as 0.5 and 0.07 for separations of 0.2 and 2 microns, respectively. The output quantum efficiency of the laser amplifier was demonstrated to be comparable to the output quantum efficiency of a single oscillator. Tests of a new structure for a low-noise, constant-gain laser amplifier are described.

Error-controlled high power linear amplifiers at VHF

Abstract: Two amplifiers, each covering a different band in the VHF range, were constructed for test set applications. These amplifiers were required to meet stringent specifications beyond the general scope of previous art. These specifications related to the simultaneous availability of relatively large output power, tight linearity, minimal delay distortion across a 40 per cent band, high input and output return loss, large dynamic range, and time stability. The performance problems were solved by using: (i) Quadrature couplers in a corporate structure array to provide a high multiplicity of “paralleled” transistors, yielding both the power and return loss capabilities. (ii) The emitter follower configuration as the basic amplifier element, providing broad band, high level performance owing to the large self degeneration of that configuration. (iii) A “feed-forward,” instead of a feedback, system for error control and noise cancellation.

PARAMETRIC AMPLIFICATION OF ULTRASONIC WAVES IN CdS

Abstract: Traveling‐wave parametric amplification of 0.5‐GHz acoustic shear waves has been observed in CdS at room temperature. Acoustoelectric coupling provides the nonlinear interaction. Observed gain was about 10 dB/mm, which is comparable to that of the conventional acoustic amplifier.

High-efficiency power amplifier

Abstract: Described is a high-efficiency Class B power amplifier which operates at essentially 100 percent efficiency for all output voltages, either direct current or alternating current. This is accomplished by utilizing in the amplifier switching transistors in combination with chokes, the arrangement being such that unwanted voltages appear across the chokes at any instant. The chokes, being energy storing devices, can deliver their stored energy to the load after the transistors are turned off.

Noise Loading Analysis of a Third-Order Nonlinear System with Memory

Abstract: This paper presents the noise loading analysis of a third-order nonlinear system characterized by Volterra kernels. The analysis is of practical interest since intermodulation distortion is often a limiting consideration in the design of solid-state long-haul broad-band frequency-division multiplexed transmission systems, and since speech on such systems is best represented by zero mean Gaussian noise. The analysis technique is amenable to digital computer calculation; as such, quantitive results are readily obtained. The analysis was applied to a single-stage transistor amplifier that was represented by a frequency-dependent nonlinear model. An excellent agreement between measured and calculated results was obtained. Portions of the program written for this example are readily applicable to the calculation of intermodulation distortion for any thirdorder nonlinear system (e.g., amplifier, repeater, or cascade of repeaters and cable sections) given the appropriate Volterra kernels.

Apparatus and method for controlling the power supplied to a load

Abstract: A method for controlling the power supplied to a load and an apparatus to accomplish this, comprising: a means for monitoring the voltage supplied to the load; a voltage squaring circuit adapted to generate a control signal proportional to the average value of the square of the voltage; and a proportional controller adapted to compare the control signal with a reference signal and to proportionally control the power supplied to the load. The proportional controller comprises: a control amplifier, adapted to convert the DC control signal to an AC signal and to amplify the AC signal; a novel demodulating circuit; and a proportional band adjustment.

Industrial process control apparatus

Abstract: A computer-operated process control system wherein a high-speed digital computer receives a plurality of condition measurement signals such as pressure, temperature or the like, and produces a corresponding series of command signals for controlling respective process valves to positions providing stable operation of the process. The command signals in the disclosed embodiment are in the form of pulse-duration signals which are directed to electronic circuits each arranged to produce a continuous DC signal representing the desired position of a corresponding valve. The DC signal level is determined by the charge on a capacitor connected in the feedback circuit of an operational amplifier, and the command signal is operative to adjust the capacitor charge as required by the computer computations. Each capacitor with its associated amplifier serves as a memory device to maintain the valve signal at a set level while the computer is occupied in performing the remainder of the program cycle for the other process conditions.

Sound viewer apparatus

Abstract: A sound viewer apparatus is described, including means for receiving an audio signal and converting it into an electrical signal, at least one amplifier for adjusting the intensity level of the electrical signal; a plurality of filters, each having a band-pass corresponding to the major frequency components of the audio signal produced by a particular device (viz a car engine, train whistle, horn or emergency vehicle siren); indicator means, such as lamps, connected to the output of the filters; and automatic gain control means responsive to the output of each filter for adjusting the electrical signal input to the amplifier for maintaining the input to the indicators at a level whereby the indicator means (lamps) can clearly show, by relative brightness, which type of device produced the audio sound and its relative intensity.

A high-power, untuned radio-frequency transmitter for pulsed nuclear magnetic resonance spectroscopy

Abstract: A gated radio-frequency transmitter suitable for pulsed nuclear magnetic resonance spectroscopy is described. It has a wide frequency response (3 dB from about 20-50 MHz) and can deliver pulses of greater than 900 v peak to peak into 180 Ω resistive loads with rise and fall times of less than 01 μs. The circuitry described includes a gated radio-frequency mixer-amplifier with two variable phase inputs, and a gated radio-frequency power amplifier. The gating circuits used are d.c. coupled throughout to prevent droop in long pulses and interaction between the pulses.

Automatic gain control rf-if amplifier

Abstract: Disclosed is a differential amplifier circuit featuring electronic gain control, and this circuit may be constructed in monolithic integrated form. In one embodiment of the invention, first and second pairs of differentially coupled transistors are connected respectively to first and second differentially coupled input transistors, and the input transistors are connectable to a source of differential input signals. Differential output signals are derived at the outputs of transistors in each of the pairs of transistors, and by applying an automatic gain control (AGC) signal at a node which is common to the transistor pairs, electronic gain control is obtained without a differential signal arising therefrom. In another embodiment of the invention, an output differential amplifier stage is directly coupled to transistors in the first and second pairs of transistors so that any common mode signal present there is rejected in said output stage.

Linearization of radiation gauges for measuring the quantity of fluidic materials in containers

Abstract: Specifically disclosed is a method and apparatus for linearizing the output of a nuclear radiation tank level gauge. A plurality of radiation detectors are vertically spaced along one side of the tank to produce separate signals which are fed to a summing amplifier and a point source is located on the opposite side of the tank. The summing amplifier has individually adjustable input resistors whereby each signal is individually weighted to produce an amplifier output signal which is linearized with respect to the liquid level in the tank. For standardization, when the liquid level is below the top detector, the signal from the top detector is separately fed to the amplifier input in substitution for the multiple input signals, and the gain of the measuring system is adjusted to compensate for changed parameters of the system.

Integrated frequency selective circuit and demodulator including phase locked loop

Abstract: AN INTEGRATED FREQUENCY SELECTIVE CIRCUIT PARTICULARLY USED FOR DEMODULATING AN FM SIGNAL WHICH INCLUDES A PHASE LOCKED LOOP HAVING A PHASE COMPARATOR COUPLED TO A LOW PASS FILTER AND AMPLIFIER WITH IN TURN HAS AN OUTPUT VOLTAGE WHICH IS THE DESIRED DEMODULATED INPUT SIGNAL AND IS COUPLED TO A VOLTAGE CONTROLLED OSCILLATOR. THE FREQUENCY OUTPUT OF THE OSCILLATOR PROVIDES THE OTHER INPUT TO THE PHASE COMPARATOR TO COMPLETE THE LOOP. WITH THE USE OF THE PHASE LOCKED LOOP, TOLERANCE VARIATIONS GREATER THAN 10% IN INTEGRAL CIRCUIT ELEMENTS CAN EASILY BE TOLERATED. BACK TO BACK DIODES MAY BE INCORPORATED IN THE CIRCUITS TO PROVIDE LIMITING ACTION FOR IMPROVED INTERFERENCE REJECTION.

Laser device with selective oscillation

Abstract: A laser oscillator of more than two stable states includes a closed loop optical circuit including a laser amplifier, and two light absorbers, the latter being, for example, GaAs PN junctions. Means such as an independent light source or voltage triggers are provided for selectively emphasizing a light beam of at least one specific propagation direction, thereby reducing the absorption coefficient and generating a stable oscillation state in that propagation direction.

Synthesis of Rational Transfer and Admittance Matrices with Active RC Common-Ground Networks Containing Unity-Gain Voltage Amplifiers

Abstract: Necessary and sufficient conditions exist, which show that only a subset of all rational matrices can be realized as the transfer or admittance matrix of a common-ground network of resistors, inductors, capacitors, and grounded unity-gain voltage amplifiers (VGUGAs). This paper shows that by eliminating the ground constraint on the amplifiers (VUGAs) one can realize any rational transfer or admittance matrix with a common-ground RC :VUGA network. The synthesis is based upon a simple circuit whose transfer function is the ratio of two independent admittances. This is used with one capacitor and one resistor to form a differentiator. The differentiators are cascaded to form an admittance polynomial whose coefficients are determined by RC products. Transfer functions are realized by forming ratios of these polynomial admittances. The synthesis procedure results in selecting component values by inspection and permits tuning the circuits with the resistors.

Automatic timing network for camera shutters

Abstract: A camera shutter timing network includes a photoconductor connected in series with a plurality of diodes, the voltage across the diodes which is a logarithmic function of the photoconductor incident light is amplified by a variable gain amplifier to produce a first voltage. A second diode network combined with variable resistors and an amplifier produces a second voltage which is a logarithmic function of the camera diaphragm opening and film speed rating. A memory capacitor is charged to the difference of the two voltages and a timing capacitor is charged through a diode type logarithmic expansion network at a constant rate dependent on the memory capacitor voltage. An electromagnet energized through a Schmitt type switch releases the shutter to closing upon a predetermined voltage on the timing capacitor. A meter indicates the difference between the first and second voltages and hence the shutter speed.

Photodiode preamplifier circuit for a card reader system

Abstract: A photodiode preamplifier circuit including input terminals to which a photodiode may be connected. The photodiode senses the presence of a mark or a hole on a sense card and in turn provides a change in voltage at a control transistor to which the photodiode is connected. An output transistor is connected to the control transistor and is conductively controlled by the signal applied to the control transistor to in turn provide an output signal at one or the other of two binary levels. A reference level control means is connected between the control transistor and the input terminals of the amplifier and responds to current variations in the control transistor to produce a compensating current to the photodiode. This compensating current maintains a constant DC voltage level with reference to a constant threshold level at the output transistor.