Showing papers on "Amplifier published in 1972"

Frequency limitations of active filters using operational amplifiers

Abstract: There are many active RC networks that implement the low-pass filter characteristic. It has been the common practice to compare these networks with regard to passive element sensitivities while assuming the amplifier to be ideal. Such an assumption gives results that disagree with experimental observations, particularly when the pole magnitudes are large. This paper characterizes the amplifier by a one-pole rolloff model and discusses the ensuing limitations on four widely used low-pass realizations. The amplifier's open-loop gain-bandwidth product is used as a parameter to generate complex-pole loci that graphically display the effect of the nonideal amplifier. The expression of the slope of these curves at the nominal pole positions is derived and first-order estimates for the resulting changes in the \omega_{0} and Q of the poles are given. These expressions can be used to determine the upper bound on the frequency \omega_{0} that these networks can effectively realize. Experimental results agree with the predicted changes. The methods have also been applied to high-pass, bandpass, band-reject, and other realizations.

Storage array and sense/refresh circuit for single-transistor memory cells

Abstract: For the cell layout in silicon-gate technology a storage capacitor is proposed that uses a field-induced nonequilibrium inversion layer as an electrode. As a sensitive refresh amplifier a gated flip-flop that can be used for one digit line at each of its two input nodes is presented. Different cells and refresh circuits have been realized in silicon-gate technologies. Cells with an area of 1600 /spl mu/m/SUP 2/(2.6 mil/SUP 2/) have been successfully operated with a READ/WRITE cycle time of 350 ns (storage capacitance 0.134 pF, digit line capacitance 0.32 pF for 64 cells per line or 128 cells per amplifier).

Clocked bootstrap inverter circuit

Abstract: A clocked bootstrap inverter circuit including an inverting amplifier, an active load for the inverting amplifier including a capacitive bootstrapping circuit, a biasing circuit responsive to a first clocking signal and a second clocking signal 180* out of phase with the first clocking signal, and an amplifier disabling device responsive to a third clocking signal which is more than 180* out of phase with the first clocking signal. The biasing circuit alternately activates and inactivates the active load while the disabling device alternately disables the amplifier and provides a small time delay for allowing the bootstrapping circuit to be precharged.

Acoustic abatement method and apparatus

Abstract: An acoustic receiver, amplifier and transmitter generate an anti wave which is in-phase and of mirror symmetry with respect to a propagating acoustic wave. Coherent propagation means such as an acoustic duct of particular dimensions redirects and/or converts the acoustic wave and the anti wave, which otherwise propagate with incremental wavefronts at different vectors, into plane waves which are superimposed to create wave interference which itself propagates. For noise of high sound pressure level such as created by a gas turbine engine, the acoustic transmitter comprises a modulated gas flow speaker coupled to one or more bleed ports which supply gas at one or more pressures offset from ambient pressure.

Cross modulation and intermodulation in amplifiers at high frequencies

Abstract: Cross modulation and intermodulation in amplifiers at high frequencies are investigated using the Volterra series approach. The general relationships between these forms of distortion are defined and the importance of phase in the specification of cross modulation is discussed. The use of feedback for distortion at high frequencies is investigated and it is shown that appropriate control of the feedback loop phase shift can result in substantial reductions in cross modulation over broad bandwidths. All theoretical conclusions are verified by circuit measurements at frequencies up to 200 MHz.

Optical measuring apparatus

Abstract: A narrow laser beam is directed towards a mirror which is rotated to effect rotary planar scanning or sweeping of a lens constructed to convert the rotary scanning beam into a parallel scanning beam. An article to be measured is positioned in the path of the parallel scanning beam at generally the focal point of the lens, and the interruptions of the parallel scanning beam, as produced by the article, are sensed by a photodetector. The photodetector transmits corresponding pulses or signals through an amplifier to an edge decoder which receives a reset signal with each pass of the scanning beam. The edge decoder may provide for selecting different combinations of signals received from the amplifier to control the counting of constant pulses received by a counter from a high frequency generator or clock so that the counted pulses correspond to the dimension of the article at the plane of the parallel scanning beam. Preferably, the motor which rotates the scanning mirror is supplied with electrical energy from the clock through a frequency divider, and the amplified signals from the photodetector are compared with a reference level to provide an automatic gain control for the amplifier.

Large-signal noise, frequency conversion, and parametric instabilities in IMPATT diode networks

Abstract: A theoretical treatment is presented of some of the nonlinear properties of the IMPATT or Read avalanche diode, a negative-resistance semiconductor device that is now coming into wide-spread use for microwave oscillators and power amplifiers. Based upon the somewhat idealized Read model, this theory presents a qualitatively meaningful explanation of certain "parametric" effects that are often troublesome to the designers of amplifier and oscillator networks. First, an analytic treatment is given for frequency-conversion effects that appear when the device is strongly driven by one continuous signal, and simultaneously perturbed by a weak signal at another frequency or by noise. From this theory, stability criteria are derived for spurious oscillations of the "parametric" type which frequently appear in these devices under large-signal conditions. The noise-generation mechanism is reviewed, and it is shown that the noise is enhanced by strong signals and the spectral distribution is modified by frequency conversion. Some measurements of noise and frequency-conversion gain are presented which indicate substantial qualitative agreement with the theory.

Touch sensitive electronic switch

Abstract: In order to provide sensitive, touch responsive electronic switching, a pair of electrodes disposed in a unique configuration are coupled to a high gain amplifier such that relatively high resistance bridging across the electrodes will result in a positive switching condition at the output terminals of the high gain amplifier. In a first preferred embodiment of the invention, the pair of electrodes comprises a first centrally disposed electrode encompassed by a second, circular electrode disposed concentrically to, but longitudinally offset from the first electrode. Thus, the pair of electrodes substantially conform to the contour of an operator's finger which sets up a relatively high resistance path between the two electrodes when both are touched. The finite galvanic skin resistance is sensed and differentiated from the substantially infinite resistance normally existing between the two electrodes by high current gain amplification to provide a sharp change in current flow through a load connected to the output terminals of the high gain amplifier. The sharply differentiated state of the output terminals of the high gain amplifier may be utilized to control switching functions in any manner desired in subsequent stages. For use in environments in which the atmosphere may be contaminated or which may require the use of gloves by the switch operators, a membrane which has, on its underneath side, a conductive coating, is disposed over the pair of electrodes to perform the bridging function when the membrane is pressed against the electrodes.

Closed‐cycle performance of a high‐power electric‐discharge laser

Abstract: The performance characteristics of a large‐volume CO2 electric‐discharge convection laser operating in a closed‐cycle mode are described. The use of a combined dc and rf excitation field and aerodynamic stabilization techniques resulted in the attainment of a stable and homogeneous discharge. Operating in a master oscillator‐power amplifier mode, continuous‐output power levels greater than 20 kW have been achieved for extended periods of time, with a maximum optical power of 27.2 kW at an efficiency of 17.2%.

Vortex-type mass flowmeters

Abstract: A vortex-type mass flowmeter for measuring the mass of fluid passing through a flow tube as well as the density thereof. A bluff body, swirl blades or other means disposed within the tube acts to create a pulsatory fluidic vortex therein whose frequency varies as a function of the volumetric flow rate of the fluid being measured. Placed within the flow tube is a pressureresponsive transducer adapted to generate an electrical signal whose frequency is proportional to the fluidic pulse rate and whose amplitude is a function of the kinetic energy contained in the vortex. The transducer signal is processed by an operational amplifier, the gain of which is inversely proportional to frequency, thereby effectively dividing the transducer signal by frequency throuhgout the operating range of the meter to yield an output signal whose amplitude is indicative of mass flow. By additionally dividing this output signal by frequency with a second amplifier having a gain which is inversely proportional to frequency, a signal indicative of the fluid density is produced.

High-Q factor insensitive active RC network, similar to the tarmy-ghausi circuit but using single-ended operational amplifiers

Abstract: A high Q, insensitive, active RC network, usable up to several megacycles, is described. It has similar properties to the circuit proposed by Tarmy and Ghausi, but uses operational amplifiers with single-ended output terminals. The circuit can be realised with only two amplifiers; using three, the two capacitors required can be earthed.

Coherent sampled readout circuit and signal processor for a charge coupled device array

Abstract: A coherent sampled CMOS readout circuit and signal processor coupled to a CCD shift register operated by a two-phase minority carrier transfer clock system. The invention comprises a multiplex MIS switch, a reverse biased collection diode, an N channel MOSFET reset switch, a P channel MOSFET electrometer amplifier, and a sample and hold circuit, the configuration having four distinct operational timing sub-intervals within a clock period wherein the charge is shifted from one shift register bit to another and finally to the output bit. This removes the Nyquist noise associated with the reset switch, suppresses switching transients and 1/f surface noise to thereby improve the signal to noise ratio, i.e., dynamic range, for a CCD array and readout system.

Use of Four-Level Phase Modulation for Digital Mobile Radio

Abstract: The paper explains the advantages of and compares various forms of four-level phase modulation from the point of view of performance, implementation, and spectrum usage. The results are applicable to digital mobile radio systems employing a large number of transmissions in which cochannel and adjacent channel interference are experienced. Of particular interest is the extent to which the theoretical spectra may be realized with practical transmitters. Differences between theoretical spectra and those measured from practical power amplifiers are identified. A method of simulating the effects of power amplifier nonlinearities is described and results are presented which agree closely with measurements made on an actual power amplifier.

Switching voltage regulator with input low voltage and output voltage detectors

Abstract: A constant potential power supply having a Schmitt trigger regulator and switching amplifier to maintain the output load voltage within a predetermined range, and an undervoltage protection circuit which disables the regulator when the input potential goes below a predetermined level. An integrating capacitor which is part of the Schmitt trigger regulator, discharges through the load. The Schmitt trigger regulator is actuated when the output potential decreases below a certain maximum value and is disabled as the output potential goes below a certain minimum value; it is also actuated when the output potential increases to this minimum value and is disabled as the output potential goes below this maximum value. After actuation and until disabled, charging current is applied to the capacitor. The switching amplifier circuitry, which is coupled to the output load and the regulator, enables and disables the line switch of the regulator when the output voltage increases to this minimum value and when it decreases below this same minimum value. The output triggering section of the regulator disables the line switch when the output voltage increases above this maximum value and when it decreases below this same maximum value. The particular arrangement between the switching amplifier and the regulator provides significant control of the hysteresis as well as decreasing it and improving the overall regulation of the circuit.

Orally operated electronic musical instrument

Abstract: Means forming an air channel is connected between the output of a loudspeaker and the input of a microphone. The output of the microphone is amplified by means of an amplifier, the output of the amplifier being fed to the speaker, an acoustical feedback path thus being formed between the speaker and the microphone. A mouthpiece is connected in this acoustical path such that an operator can determine the frequency of the feedback signal by adjusting the size of his oral cavity, thus forming musical tones.

In ear hearing apparatus

Abstract: A hearing apparatus equipped with an output transducer, a voltage source, an amplifier, an input transducer capable of magnetic or electrical reception and a gain control. There is provided an elongate bipartite housing constructed to be inserted into the auditory or hearing channel. In the lengthwise direction of the housing there are arranged adjacent to one another the output transducer, the voltage source, the amplifier, the input transducer and the gain control. The output transducer is arranged in a first part of the housing, the amplifier, the input transducer and the gain control are arranged in a second part of the housing which is detachably connected with the first part of the housing. The voltage source is arranged between the output transducer and the amplifier at the region of the connection location of the housing parts.

Gas gain measurements in proportional counters

Abstract: Doubt is cast upon evidence in favour of various theories of gas amplification because of errors in gas gain measurement through amplifier pulse shaping effects. Measurements for a 90:10 Ar:CH4 gas mixture are presented which illustrate this effect.

Light amplifier using a semiconductor

Abstract: A light amplifier using a semiconductor, in which an elongated single semiconductor PN junction is used for amplifying an input light injected at an input face provided at one end of the PN junction along the junction plane of the PN junction. The semiconductor PN junction is driven by bias signals applied at a common ohmic electrode and a plurality of ohmic electrodes respectively provided at opposite sides of the PN junction with respect to the junction plane. A plurality of the ohmic electrodes are sequencially arranged overlying the PN junction in a longitudinal direction and are electrically isolated from one another, so that a plurality of discrete regions are provided in the PN junction corresponding to the respective electrodes. Two adjacent regions are employed as one unitary region and are driven by predetermined different forward bias currents to bias one of the two regions as an amplifying region and the other of the two regions as a saturable absorbing region. The amplifying region is disposed at the input side while the saturable absorbing region is disposed at the output side in each unitary region. The respective unitary regions are connected in cascade to provide a plurality of the unitary regions.

Gyrator employing field effect transistors

Abstract: A gyrator circuit of the conventional configuration of two amplifiers in a circular loop, one producing zero phase shift and the other producing 180* phase reversal. All active elements are MOS field effect transistors. Each amplifier comprises a differential amplifier configuration with current limiting transistor, followed by an output transistor in cascode configuration, and two load transistors of opposite conductivity type from the other transistors. A voltage divider control circuit comprises a series string of transistors with a central, voltage input to provide control, with locations on the amplifiers receiving reference voltages by connection to appropriate points on the divider. The circuit produces excellent response and is well suited for fabrication by integrated circuits.

Floating negative-impedance converters

Abstract: Two floating negative-impedance converters (FNICs) using operational amplifers are proposed. Each circuit uses a common-grounded power supply and can simulate floating negative elements. The stability properties of the two circuits are examined. In line with other published grounded NICs, one of the ports is found to be short-circuit stable and the other open-circuit stable. The application of the FNICs for the design of two-directional constant-resistance amplifiers is considered.

Sound reproducing system utilizing motional feedback

Abstract: A sound reproducing system utilizes motional feedback to reduce loudspeaker distortion and to extend the loudspeaker''s frequency response. The system substantially comprises an amplifier which is jointly responsive to the input source signal and to a feedback signal, a moving-coil loudspeaker including a main electromagnetic structure which is responsive to the amplifier''s output signal for effecting axial speaker-cone motion, motional sensing means for providing a signal which is functionally related to axial cone velocity, and an equalizer exhibiting a predetermined nonlinear attenuation versus frequency characteristic and which is responsive to the motional signal for providing the feedback signal. The feedback signal is degeneratively applied to the amplifier which, in turn, forces the loudspeaker to respond linearly to the input source signal and thereby provide a uniform sound energy output. It is a feature of the present invention that the loudspeaker cone exhibits a substantially constant acceleration at low frequencies and a substantially constant velocity at higher frequencies.

Differential amplifier having active feedback circuitry

Abstract: Common-mode and differential-mode active electrical and electrooptic feedback systems are formed with a plurality of physically interchangeable circuits. One of a plurality of input stage amplifiers can be connected to one of a plurality of loads through intermediate and output stage amplifiers. A plurality of interchangeable feedback stage amplifiers are then connected from various stage amplifiers back to the input stage amplifier. Such arrangements control the gain and the input and output impedances of the system independently for both the common and differential modes.

Field effect transistor detector amplifier cell and circuit for low level light signals

Abstract: A light sensitive element, typically a phototransistor, diode or the like, is suitably coupled to a load element, typically an FET device suitably biased as a linear load. An output circuit including a high input impedance element, typically an FET inverter, is coupled between the linear load and the diode. Little or no current flows in the input circuit in the absence of light applied to the light sensitive element. When light is applied current flows through the light sensitive element and modulates current flow through the inverter. The output circuit has high sensitivity to low level light signals by reason of the linear load and the absence of "Johnson" or thermal noise. A suitable connection between the light sensitive element and the load element sets the output circuit in a threshold state for immediate response to light signals. Connecting the inverter output to suitable circuitry, i.e., amplifiers, differential amplifiers, level shifters and the like, provides an analog or digital output sensitive to extremely low light levels.

Analog transmission gate

Abstract: A transistor switching network, responding to a logic input, switches current selectively into one of a number of nodes, each node connecting a pair of bipolar transistors coupled differentially in a unity gain amplifier circuit. From a number of analog input signals applied to the differentially connected transistor pairs, only the one coupled to the selected node will produce an output from the voltage follower circuit. Conversely, a single analog input signal may be gated selectively to any one of a number of output terminals.

Visual-audio device

Abstract: A picture frame with a picture of a person mounted therein, a housing secured to the rear of the frame and a sound producing mechanism mounted in the housing for reproducing utterings made by the person. The sound producing mechanism includes a length of tape on which utterings made by the person are recorded and a tape storing and driving mechanism for driving the tape in a path along which a tape pickup head is situated. An amplifier is electrically connected between the tape pickup head and a speaker; and a switch is connected to the sound producing mechanism for energizing and de-energizing the same.

Optical range finding system

Abstract: An optical range finding system wherein a local frequency component of the image of an object is generated and the position of the plane of maximum amplitude of the frequency component is established by an objective to produce the image, a grating located in the image space, a beam splitter for splitting the image into two components and photoelectric detectors receiving radiation which has been modulated by the grating. The radiation constitutes at least part of each of the frequency components and the detecting means supply signals to a push-pull amplifier having a frequency equal to the local frequency. These signals are indicative of the position of the plane of maximum amplitude.

Fuel supply systems for internal combustion engines

Abstract: An electronic governor, particularly for a diesel engine has a summing amplifier receiving signals representing the output of the pumps supplying fuel to the engine, engine speed, and engine demand. The summing amplifier serves to produce an output for operating the pump in accordance with predetermined engine current characteristics. A second summing amplifier may be used to override the first summing amplifier to limit maximum fuel. Alternatively, the first summing amplifier may compare demanded fuel supply with actual fuel supply, in which case the second amplifier sets the maximum speed.

Practicable X-Ray Amplifier

Abstract: Inverted populations of practical interest in the x-ray region are obtainable from selective inner-shell vacancy production in intermediate-energy ion-atom collisions. A high-current ion beam swept at nearly the speed of light along the length of an extended foil provides an active region in synchronization with a resonant x-ray pulse traveling parallel to the foil surface. Significant amplification may be realized with presently available ion sources.

Predistortion compensation for a microwave amplifier

Abstract: A predistortion circuit for compensating distortion in a final amplifier includes a first directional coupler for separating a portion of the input modulated microwave signal into first and second channels having first and second signal components therein, respectively. The second signal component is fed to a distortion amplifier having a distortion transfer characteristic substantially similar to that of the final amplifier to be corrected. The distorted output of the distortion amplifier is proportioned in amplitude by a variable attenuator and combined in phase opposition with the larger undistorted first microwave signal in a second directional coupler to form a composite predistortion microwave signal having distortion components inverted in phase relative to thephase of the undistorted components. The distortion components in the composite predistorted input signal to the amplifier cancel the distortion components introduced by the final amplifier to produce an output signal in the final amplifier having substantially reduced distortion components.

Method of and means for gain-ranging amplification

Abstract: A gain-ranging amplifier is disclosed comprising a plurality of fixed gain amplifier stages connected in cascade and means for taking the output signal from any one of the fixed gain amplifier stages. Control means are described whereby such output signal is taken from the amplifier stage immediately preceding the first such stage which is being overdriven at a particular point in time by the signal which is being amplified. Specific circuits are disclosed for use in seismic geophysical exploration applications and means for generating a signal representative of the amount of gain utilized in amplifying the input signal and for monitoring the input signal are described.