Showing papers on "Amplifier published in 1978"

Effects of circuit variations on the class E tuned power amplifier

Abstract: The operation of the class E tuned power amplifier may be described by a set of equations based on Fourier component analysis. Previous publications have derived an optimum operating mode in which the collector efficiency of an idealized circuit is 100 percent. Since real amplifiers are made from nonideal components and are subject to nonideal loads, it is necessary to determine the effects of deviations from the ideal. The effects of variations in component values and duty cycle are determined from the basic equations. Numerical results of variations in load reactance, shunt capacitance, load resistance, frequency, and duty cycle are presented. The amplifier was found to be quite tolerant of reasonable circuit variations. With proper output filtering, the amplifier can be operated over nearly an octave bandwidth with less than a 5 percent reduction in efficiency.

Transistor power losses in the class E tuned power amplifier

Abstract: The class E switching-mode tuned power amplifier offers efficiency approaching 100 percent. It is especially applicable at high frequencies because it minimizes the power dissipated during the switching transitions, even if the switching time is an appreciable fraction of the signal period. When the amplifier is properly loaded and tuned, power losses are caused primarily by active-device saturation voltage and resistance, nonzero switching time, and lead inductance. An accurate estimation of the dissipated power is presented giving more accurate circuit and thermal designs.

Suppression of self-focusing through low-pass spatial filtering and relay imaging.

Abstract: Self-focusing effects in large, high power laser amplifiers become manifest as small-scale beam instabilities and as large-scale phase aberrations. Spatial filtering has been shown to control instabilities; spatial filters constitute appropriate lens pair elements for image relaying as well. In this paper, image relaying is presented as a technique for preserving the transverse intensity profile of a high power beam as it propagates long distances through nonlinear elements. As a consequence, amplifier apertures can be filled more effectively, leading to a doubling of fixed-aperture system performance. A rationale for optimal selection of spatial filter bandpass is also presented. This selection, as might be expected, depends upon details of the beam's spatial structure as it enters any filter. A geometrical optics approach is used throughout; nevertheless, derived results remain valid when diffraction is included.

Characteristics of integrated MOM junctions at DC and at optical frequencies

Abstract: We present a new metal-oxide-metal device (Ni-NiO-Ni, "Edge MOM") which is stable, reproducibly fabricated, and with a 10-10-cm2tunneling area. Performing detection experiments, the device's nonlinear I-V characteristic is shown to be invariant at audio frequencies, 10.6, 3.39, and 0.6328 μm. Similar devices with 10-8-cm2tunneling areas perform as well as the Edge MOM's in the visible and the near-infrared range, but deteriorate in performance at the 10-μm range. A dominant competing effect is a thermal-induced signal, which increases with frequency and temperature. Coupling mechanisms at the various regimes are investigated. The device can serve as a broad-band detector and mixer, and might in the future be a basic element of broad-band amplifiers and oscillators.

Object identification system

Abstract: An object identification system comprising a frequency sweep generator which generates an interrogation signal to be transmitted by the transmitter; a response device, consisting of passive resonance elements, mounted on the object to be identified; a receiver for receiving the reply signals; a phase shifter connected to the output of the frequency sweep generator; phase detector which compares the output of the receiver with the phase shifter output; and the series connection of a low pass filter, amplifier, and Schmitt circuit connected to the output of the phase detector in order to detect the steep phase variation of the signal received from the object.

Illumination signal processing system

Abstract: Control of illumination with illumination amplifier devices provides a basis for implementing various types of illumination systems. Also illumination amplifiers in closed illumination servo loops provide improved illumination control. An illumination control system provides precise control of camera operations for photographic and photoplotter applications. Illumination amplifier devices are used in conjunction with electronic control circuits to provide flexibility and precision in camera systems, reducing reliance on prior art mechanical devices. Illumination control circuits are presented in the form of digital gates and flip-flops and in the form of analog computational elements to provide illumination computer systems. In addition, a batch fabricated illumination computer arrangement is presented for improved implementation of illumination control systems. Illumination amplifiers are further configured for control of illumination in buildings and automobiles. Various types of devices such as windows, shutters, shades and visors are configured with illumination amplifiers to provide electronic control of illumination. Batch fabricated display arrangements are provided having an illumination source integral with an illumination amplifier for low cost, small volume, and flexibility. Also, colored display arrangements are provided for control of colors with illumination amplifier devices.

Push-pull switching power amplifier

Abstract: A true push-pull switching power amplifier is disclosed utilizing two dc-to-dc converters. Each converter is comprised of two inductances, one inductance in series with a DC source and the other inductor in series with the output load, and an electrical energy transferring device with storage capability, namely storage capacitance, with suitable switching means between the inductances to obtain DC level conversion, where the switching means allows bidirectional current (and power) flow, and the switching means of one dc-to-dc converter is driven by the complement of a square-wave switching signal for the other dc-to-dc converter for true push-pull operation. For reduction of current ripple, the inductances in each of the two converters may be coupled, and with proper design of the coupling, the ripple can be reduced to zero at either the input or the output, but preferably the output.

Small-scale self-focusing effects in a high power glass laser amplifier

Abstract: Experimental data and the results of detailed numerical calculations are presented for small scale beam breakup due to non-linear self-focusing in Cyclops, a high power Nd-glass laser amplifier. Both perturbed plane wave and nonlinear whole beam calculations were carried out. The whole beam calculations were carried out using a dust particle model of beam perturbations.

Low-noise amplification of voltage and current fluctuations arising in epithelia.

Abstract: Two low‐noise differential input amplifiers designed for voltage and current fluctuation measurements in epithelia are described. The first one uses a matched pair of low‐noise transistors and is particularly suited for low‐frequency current and voltage noise measurements in frog skin and other preparations with impedances below 1 kΩ. The second one is designed around a matched pair of JFETs and can also be used for higher source impedance. Performance is demonstrated with Na+ current power density spectra obtained from frog skin with the transistor‐input stage.

Linear amplification with nonlinear devices

Abstract: The present linear amplifier uses nonlinear components where an input signal with amplitude and phase variations is concurrently applied to a limiter (41) and an envelope detector (42) which provide signals that serve as a carrier signal and a modulating signal, respectively, to a phase modulator comprising two or more linear suppressed-carrier amplitude modulators (50) connected in cascade. The weighted carrier signal and weighted outputs of the even-numbered amplitude modulators (50 2 , 50 4 , . . . ) are added separately from the weighted outputs of the odd-numbered amplitude modulators (50 1 , 50 3 , . . . ) to generate two signals which are combined in a quadrature coupler (56). The two outputs of the quadrature coupler are separately amplified in a pair of amplifiers (60, 61) and combined in a second quadrature coupler (64) to provide a substantially linearly amplified output signal of the input signal.

A precision FET-less sample-and-hold with high charge-to-droop current ratio

Abstract: A monolithic sample-and-hold amplifier designed without field-effect transistors is described. Various sample-and-hold configurations are compared and their merits are discussed. Unique features of the design include a diode-bridge switch and a current booster with 50 mA of drive capability to charge the hold capacitor during large signal acquisition. The output amplifier's operating conditions are changed under logic control; it functions as a fast follower in the sample mode, and as a low input current amplifier in the hold mode. Performance characteristics include: 3.5-/spl mu/s acquisition time to 0.1 percent with a 5000-pF hold capacitor, 50 pA of droop current from 0 to 70/spl deg/C, 10/SUP 9/ charge-to-droop current ratio, and 0.3 mV of zero-scale error.

Monolithic CMOS digital temperature measurement circuit

Abstract: A monolithic integrated complementary metal oxide semiconductor (CMOS) circuit senses internal junction temperature and converts it to a binary coded decimal output signal. The circuit compares a temperature dependent junction voltage with a bandgap reference voltage controlled by a very stable amplifier. The comparison differential is then converted to a binary coded decimal output signal by an analog to digital converter. The circuit utilizes parasitic bipolar NPN transistor elements formed from a substrate of the chip in a conventional CMOS fabrication process. The principles of the present invention are also broadly applicable to other semiconductor technologies such as integrated injection logic (I 2 L).

Heart rate measurement system

Abstract: A pulsed IR reflectance plethysmograph for heart rate measurement and display in a digital watch or as a medical instrument using, for example, a pulsed LED light emitting diode for transmitting light pulses and a photodiode for receiving light pulses reflected from a finger. The LED and photodiode are mounted in a small sensor on the watch or medical instrument. The photodiode is connected directly to a signal conditioning circuit which rapidly removes unwanted asynchronous ambient background light signals such as from sunlight, by means of a switched ambient light subtractor circuit which performs the subtraction without requiring amplification or conversion of the detector signal photocurrent to another electrical parameter. The signal current after cancellation of the ambient background signal is sampled in an integrate and hold circuit to provide a heart systolic pressure wave. The synchronous steady state IR pulse carrier envelope signal is cancelled by a perfect second-order feedback loop via an integrating amplifier and a switched transconductance element that operates with fast response, even under conditions of large overloads that occur at the sensor. Pulses of the heart systolic pressure wave are then detected to determine the pulse rate which is displayed. When only the presence of an unmodulated IR light carrier is to be detected, as in an IR light beam detector, an ambient light subtractor in accordance with the invention is provided in an unswitched configuration that removes ambient light with a minimum number of components over an extremely wide dynamic range.

A single chip all-MOS 8-bit A/D converter

Abstract: A new analog-to-digital (A/D) conversion technique compatible with standard single channel MOS technology is described. This technique uses a string of equal value diffused resistors and a matrix of analog switches to perform high-speed successive approximation conversion. The comparator function is realized by a chopper-type amplifier to reduce the inherently high input offset voltages of MOS differential stages. Typical performance characteristics taken from a large sample of ICs are presented; a resolution of 8 bits has been achieved with a conversion time of 20 /spl mu/s. The complete system is fabricated on a 14000 mil/SUP 2/ die. Due to its small relative size, this A/D technique has been incorporated as part of a larger CODEC system.

AM Broadcast tuner with automatic gain control

Abstract: An RF amplifier stage of an AM broadcast tuner is disclosed wherein, depending upon the power level of the received input signal, said input signal is amplified by a high gain radio frequency amplifier, or by a low gain radio frequency amplifier, or by a combination of both the high and low gain radio frequency amplifiers at intermediate levels. This system provides wide dynamic range and low distortion in that it prevents amplifier saturation and reduces intermodulation product signal levels.

Arrays of Josephson tunnel junctions as parametric amplifiers

Abstract: Arrays of 10 or 40 series‐connected small densely packed Josephson tunnel junctions were successfully operated as parametric amplifiers at 10 GHz. Between 50 and 90% of the junctions in an array were observed to work coherently in the amplification process. Signal gain exceeding 24 dB was achieved with a pump power as low as −50 to −70 dBm. A power width (i.e., the range of the pump power for a gain within 3 dB of the peak gain) of 0.25 dB and a bandwidth of 15 MHz were measured for 20‐dB gain. The power width was in accordance with theory but the bandwidth was reduced, probably due to noise saturation effects. The latter effects can be reduced by lowering the input noise temperature or by including an external band limitation. The noise temperature was also increased by saturation; however, with an external bandwidth of 60 MHz, a noise temperature of 30±20 K was measured. The application of a magnetic field has proved extremely useful as a means of tuning the amplifiers to stable high‐gain operating poin...

A wideband radial power combiner for FET amplifiers

Abstract: A power combining technique for GaAs FET amplifiers will be presented. The approach, using a 12-way divider-combiner, has demonstrated a 31% 1dB bandwidth with an insertion loss of 0.25dB and a CW output power of 4.4W at 8.5GHz.

Protected amplifier apparatus

Abstract: This disclosure relates to an amplifier incorporating various devices for detecting parameters such as average power, peak power and signal voltage to be used to provide the feedback signals for automatic level control of an RF amplifier whose output signal is passed through an antenna coupler to an antenna. These detection devices allow normal operational level setting as well as minimizing the chance of overloads resulting in amplifier circuit failure during tuning conditions.

A low drift fully integrated MOSFET operational amplifier

Abstract: A fully integrated MOSFET amplifier with very low drift has been built using standard technology. Input offset voltages as low as 5 /spl mu/V and drift values of this offset voltage less than 0.05 /spl mu/V//spl deg/C are measured.

Two-Signal Method of Measuring the Large-Signal S-Parameters of Transistors

Abstract: In this paper, large-signal S-parameters are reviewed, and transistors of Class-C are employed. Problems are encountered in obtaining large-signal parameters S/sub 12/ and S/sub 21/. A novel method is concisely developed based on theory presented herein. The acquired S-parameters are applied to amplifier design accordingly. The predicted and measured output power are compared, and suitable conclusions are duly recorded.

Low power system and method for communicating audio information to patrons having portable radio receivers

Abstract: Low power apparatus and method for tuning portable receivers of patrons of an establishment (such as an auditorium) to a predetermined frequency and communicating audio frequency information to the patrons via the portable receivers An audio signal is derived from an audio frequency public address sound system and inputted to a modulator to modulate a radio frequency carrier signal The modulated carrier signal is amplified and transmitted by means of a loop antenna surrounding the region of the establishment wherein the patrons and their portable receivers are situated A very low power modulated radio frequency signal is derived from a transmitter including a modulator and an amplifier and is inputted to a receiver tuning aid circuit positioned near the entrance of the establishment The tuning aid circuit drives a small ferrite core antenna which radiates a signal which enables the patrons to easily tune their portable receivers to the carrier signal frequency by positioning the receivers close to the ferrite core antenna and tuning the receivers for the loudest audio signal

GaAs microwave MOSFET's

Abstract: GaAs microwave metal-oxide-semiconductor field-effect transistors (MOSFET's) with plasma-grown native oxides as gate insulator have been fabricated using a low-temperature magnetically controlled plasma-oxidation technique. A small-signal enhancement device with the gate length of 2.0 µm has demonstrated useful unilateral power gains in the 2-8-GHz frequency range. A maximum frequency of oscillation in the enhancement device is 13 GHz. This is the highest in all enhancement-mode GaAs devices reported up to this time. A medium-power depletion device with the gate length of 1.8 µm has the maximum frequency of oscillation of 22 GHz. This value is 10 percent larger than that of the best analogous metal-semiconductor field-effect transistor (MESFET). The intrinsic current-gain cutoff frequency for the depletion MOSFET is 4.5 GHz which is 22 percent higher than that of the MESFET. The superiority of the depletion MOSFET in the small-signal microwave performance over the MESFET results from the smaller gate parasitic capacitance in the MOSFET as compared to the MESFET. The depletion MOSFET has produced 0.4-W output power at 6.5 GHz as a Class A amplifier. Quite a large frequency dispersion of transconductance is observed in the enhancement MOSFET at a frequency range between 10 and 100 kHz and attributed to interface states. The effect of the interface states does not severely restrict the microwave-frequency capabilities of the enhancement MOSFET as well as the depletion MOSFET since the interface states are unable to follow the input-signal variations at high frequencies.

Circuit for defined current sharing between parallel-connected switching regulator modules in DC switching regulators

Abstract: This invention relates to an improvement in a circuit arrangement for defined current sharing, between parallel-connected switching regulator modules in DC switching regulators with continuous inductor current and common error amplifiers for the purpose of generating regulated DC voltage from an unregulated voltage source, the improvement comprising means in each switching regulator module, composed of an inductor, a semi-conductor switch, a free-wheeling diode and a pulse-width modulator, whereby for the purpose of controlling the pulse-width modulator a signal proportional to the time-varying inductor current of the individual switching regulator module is negatively fed back to the output signal of the error amplifier, and where the signal resulting therefrom is used to control the pulse-width of the corresponding switching regulator module.

A Monolithic 14-bit D/A Converter

Abstract: A monolithic 14-bit D/A converter using "dynamic element matching" to obtain high accuracy and good long-term stability is described. The chip, with a size of 3.1×3.2 mm, contains all elements needed except the output amplifier and a digital input latch.

Amplifier with radial line divider/combiner

Abstract: A power amplifier that divides input power among a plurality of parallel channels through a radial line divider, amplifies the power in each channel with three terminal devices, and combines the amplified power in a radial line combiner to produce an output signal. The radial line divider/combiner includes a radial transmission line having a plurality of sectors symmetrically disposed around the inner radius of a supporting annular substrate. The sectors are connected to respective three terminal devices through microstrip transmission lines, and are isolated from laterally adjacent sectors by thin film isolation resistors.

Parasitic oscillations, absorption, stored energy density and heat density in active-mirror and disk amplifiers

Abstract: We present detailed calculations of the absorption, stored energy density, and heat density distributions for these commercial laser glasses of current interest (silicate—ED-2, phosphates—EV-2, LHG-5). The form of the stored energy density distribution is shown to be important in the consideration of parasitic oscillations in active-mirror and disk amplifiers. In active-mirror amplifiers, the application of multilayer dielectric coatings has been found not to affect the threshold for bulk parasitic oscillations. Due to the unique geometry of active mirrors, amplified spontaneous emission rather than parasitics is found to limit energy storage ultimately.

Low voltage CMOS amplifier

Abstract: A CMOS amplifier having a pair of CMOS load and amplifying devices connected in series, two parallel pairs of CMOS devices with interconnected gates to form current mirrors and connected to the gate of the load MOS device to compensate the gain for variations in power supply voltage, temperature and transistor parameters, a feedback MOS device having its source-drain path connected between the junction of the load and amplifying MOS and the gate of the amplifying MOS to provide nonlinear, negative feedback, and a resistor connected in parallel with the feedback MOS device to establish an initial self-biasing voltage level for the amplifying MOS below the threshold voltage of the feedback MOS.

Drift compensated fiber optic-receiver

Abstract: The present disclosure describes an electronic circuit for use as a receiver in digital fiber-optic systems. It is the nature of such systems that considerable amplification is required at the receiving terminus to bring to useful signal levels the electrical energy provided by photodetectors in response to the light incident thereupon. However, the photodetectors and amplifiers themselves contribute noise currents which vary with temperature and operational amplifiers have a characteristic initial dc offset. Accordingly, while receivers for fiber-optic systems have been complicated and expensive, the receiver of the present invention is neither of these. It amplifies the small signals from the photodetector to a suitable level, eliminates the effects of the aforementioned dc offset, rejects any long-term drift and provides output signals of any duration from a bistable stage, which signals correspond to the original digital information transmitted by the system.

Semiconductor radiation detector

Abstract: An electrical charge amplifier including a filter circuit is AC coupled to a semiconductor (CdTe) detector and generates a voltage pulse in response to an electrical charge generated in the detector by an incident pulse of radiation. The filter allows only frequencies within a predetermined range to contribute to the voltage pulse. The selected range of frequencies is determined in accordance with the duration of the incident radiation pulse such that the voltage pulse faithfully represents the magnitude of incident radiation in spite of undersirable detector characteristics which would otherwise introduce distortions. Exemplary charge amplifier and detector structures are also described.