Showing papers on "Amplifier published in 1984"

MESFET Distributed Amplifier Design Guidelines

Abstract: In the paper, the analysis of GaAs MESFET distributed amplifiers and a systematic approach to their design are presented. The analysis focuses on fundamental design considerations and also establishes the maximum gain-bandwidth product of the amplifier.The design approach presented enables one to examine the tradeoffs between the variables, such as the device, the number of devices, and the impedances and cutoff frequency of the lines, and arrive at a design which gives the desired frequency response. Excellent agreement is shown when the theoretically predicted response of a typical amplifier is compared with computer-aided analysis results, and good agreement is shown with previously published experimental results.

Spread spectrum radio transmission system

Abstract: A communications system wherein an intelligence signal modulates the spacing of relatively narrow pulses of a fixed rate pulse train, and these pulses key on a transmitter which employs a pair of series connected avalanche mode operated transistors. These are repetitively powered via a charged coaxial delay line, and the output, appearing across a resistive load, is fed directly, or through a shaping filter, to a discone transmitting antenna. At a receiving location, the received signal is amplified by a wide band amplifier and fed through a reverse contoured filter (of the transmitting filter, if one is employed). The signal is detected via synchronous detection which locks onto the received pulse train, after which the modulation evidence by the pulse train is recovered by a low pass filter.

Design techniques for cascoded CMOS op amps with improved PSRR and common-mode input range

Abstract: Internally compensated CMOS op amps have been widely used in sampled-analog signal processing applications over the past several years. However, the popular two-stage op amp suffers from poor AC power supply rejection to one of the power rails. Two circuits are presented that overcome the power-supply rejection ratio (PSRR) problems of the earlier amplifier: one for virtual ground applications such as switched-capacitor integrators, the other for buffer applications requiring wide common-mode input range. Small signal analysis is developed for the open-loop and PSRR responses of the two amplifiers. In addition, design guidelines are suggested and test results are presented.

Receiver design for high-speed optical-fiber systems

Abstract: The technology of optical-fiber systems is advancing rapidly. Parallel to the development of long-haul telecommunication systems in the gigabits per second data rates operating in the long-wavelength region is the wide penetration of optical-fiber systems in local area networks, video trunking and distribution, sensors, etc. These diversified applications impose different and often conflicting constraints on the optical receiver. This paper re-examines the optical receiver design in view of these different requirements, namely, high receiver sensitivity, wide dynamic range, transparent to the operating bit rate, unrestricted data format, and fast acquisition time. Design tradeoffs between conflicting receiver requirements are considered in detail. In particular, the sensitivity of high-capacity long-wavelength transmission systems is emphasized. The state-of-the-art performance of photodetectors and low-noise amplifiers is discussed. We show that dark current of avalanche photodiodes (APD's) is the main factor limiting the sensitivity of long-wavelength optical receivers. In addition, as an example, we report on the design and experimental performance of a hybridized low-noise optical receiver amplifier capable of more than 2-Gbits/s operation. The input noise spectral density achieved is 9 pA/ \sqrt{Hz} with a noise corner frequency of 920 MHz, corresponding to an equivalent noise resistance of 120 Ω.

Brightness control system for crt video display

Abstract: A video brightness control system for high performance CRT displays including a buffer amplifier for receiving high speed video information and applying it to a gain control variable resistor serving as a contrast control. An ambient light sensor drives a nonlinear amplifier to provide an ambient light signal which is in proportion to the logarithm of the ambient light level over a wide range. A manual brightness control potentiometer is adjustable to provide a constant brightness signal. The video information signal, the ambient light signal, and the manual brightness control signal are added together by a summing device, with the resultant signal approximating a logarithmic characteristic. The output of the summing device is applied to a gamma correction amplifier which drives a video driver amplifier, the video amplifier, in turn, drives the CRT. The gamma correction amplifier and video driver in combination with the video transfer function of the CRT approximates an exponential transfer function, thereby creating CRT screen brightness which is an antilogarithmic function of the total video signal appearing at the gamma correction amplifier input. This results in automatic brightness control as a function of ambient light level, minimum interaction between brightness and contrast controls, and a gamma characteristic which provides a reasonable approximation to the variation of brightness difference threshold of the eye.

Pacemaker system and method for measuring and monitoring cardiac activity and for determining and maintaining capture

Abstract: A system for determining P-wave and R-wave capture in response to pacemaker supplied electrical stimuli. One embodiment includes a conventional bipolar atrial lead having a tip electrode, connected to a P-wave pace/sense amplifier and pulse output circuits within an implantable pacemaker, and a ring electrode, spaced apart from the tip electrode, connected to a P-wave sensing EGM amplifier within the pacemaker. The bandpass characteristics of the P-wave pace/sense amplifier allow detection of P-wave frequencies in the absence of atrial stimulation pulses. The bandpass characteristics of the P-wave sensing EGM amplifier allow detection of all electrical frequencies in the atrium within the bandpass chosen. Output signals from these two amplifiers are selectively telemetered to an external receiver, where the occurrence of atrial stimulation pulses and P-waves can be monitored. In operation, if constant time intervals between the monitored atrial stimulation pulses and P-wave occurrences are present, P-wave capture has occurred. In the event of variable time intervals, capture has not occurred and the magnitude of the atrial stimulation pulses can be increased until P-wave capture does occur. An alternative embodiment measures this time differential and makes the stimulation pulse adjustment automatically. Other embodiments use the same manual or automatic systems to determine R-wave capture.

Method and device for detecting a specific acoustic spectral feature

Abstract: A method and device for detecting a narrow acoustic spectral feature in a sample as described. The method uses an electrical frequency modulated (FM) signal that is obtained from a voltage controlled oscillator. The Fourier spectrum of this wave is a main frequency fc with two small sidebands at frequencies fc ±fs. This whole triplet is slowly swept in frequency by a slow sawtooth generator. The electrical signal is fed into a flat acoustic transducer; the acoustic wave is then transmitted through an acoustically active medium, i.e. the sample, and detected by another flat acoustic transducer which produces an FM signal with a superposed amplitude modulated (AM) signal if one of the sidebands overlaps an acoustic feature. This electrical signal is then demodulated to give a pure AM signal which can be phase sensitive detected by using a lock-in amplifier. By suitable adjustment of the phase setting of the lock-in amplifier both the "in-phase" and "out-of-phase" signals of the detected acoustic signal can be detected.

System Optimization for Improved Accuracy in Transcutaneous Signal and Power Transmission

Abstract: A stable transcutaneous transmission of power and signal via two coupled coils with minimized dependence on the relative spacing of external and implanted coil is possible by employing "critical coupling" between implanted and external circuits. Optimizing coil geometries and preventing the RF output amplifier from saturating is necessary to approximately maintain critical coupling despite placement tolerances within a reasonable range. Based on these considerations a transcutaneous signal transmission system for an auditory prosthesis has been designed. This transmission system can also be used for several other stimulation purposes needing accurate control of stimulation parameters.

Temperature compensated automatic output control circuitry for RF signal power amplifiers with wide dynamic range

Abstract: Improved temperature compensated, automatic output control (AOC) circuitry for RF signal power amplifiers is described that maintains the output power within one-half dB of a selected one of eight power levels varying from nine milliwatts to five watts, a dynamic range of twenty-eight dB. The amplification of the RF signal amplifier is proportional to a drive current signal provided by a current amplifier. A half-wave rectifier is coupled to the output of final amplifiers for generating an output power signal that has a magnitude proportional to the output power. The half-wave rectifier is temperature compensated for and biased by a diode coupled to the rectifier by one resistor and coupled to supply voltage by another resistor. The output power voltage is further coupled to an amplifier having an amplification factor selected by level control signals. The amplified output power signal is coupled to a comparator which varies the drive current provided by the current amplifier in response to the voltage difference between the amplified output power signal and a reference voltage.

Bolometers: ultimate sensitivity, optimization, and amplifier coupling.

Abstract: Theoretical expressions for Johnson noise and thermal noise in bolometers are considered, and optimization with respect to thermal conductivity and bias power is performed. Numerical approximations are given for the ultimate NEP of bolometers as a function of material parameters and compared with photon noise including photon correlations. A resonating capacitor is shown to improve the coupling to an amplifier, so that the amplifier need not limit performance even for very low temperature bolometers.

Optical Processor For Phased-Array Antenna Beam Formation

Abstract: The increasing need for rapid steering of antenna beams has prompted significant research and development efforts in phased-array technology. Advances in solid-state power amplification now make it possible to construct arrays with individual amplifiers at each radiating element. Consequently, the power loss in the beam-forming network is greatly reduced, since it operates in the low-power regime. Traditionally, beam-forming and steering are performed by individually controlled phase shifters and variable gain amplifiers in the signal path of each array element. Waveguide power splitters distribute the signals to the input ports of the antennas.

Development of high density readout for silicon strip detectors

Abstract: A compact readout for silicon strip detectors is being developed. It employs an nMOS circuit with 128 channels of charge sensitive amplifiers and multiplexed output.

A Micropower CMOS-Instrumentation Amplifier

Abstract: A CMOS switched capacitor instrumentation amplifier is presented. Offset is reduced by an auto-correlation technique and effects due to charge injection are attenuated by a special amplifier configuration. The circuit which is realized in a 4 ?m double poly process has a typical offset (?) of 370 ?V, an RMS input referred integrated noise (0-f c /2) of 79 ?V and consumes only 21 ?W (f c = 8 kHz, V DD = 3 V).

Self-Consistent GaAs FET Models for Amplifier Design and Device Diagnostics

Abstract: A procedure has been developed for producing accurate and unique small-signal equivalent circuit models for carrier-mounted GaAs FET's. The procedure utilizes zero drain-source bias S parmeter tests to determine accurate values of carrier parasitics, and dc measurements to evaluate the FET's gate, source, and drain resistances. Subsequent S-parameter measurements at full bias are then used to resolve the FET into an equivalent circuit model that has only 8 unknown elements out of a possible 16. A technique for evaluating the frequency range of accurate data is presented and the FET model shown is useful well above the maximum frequency of measurement. Examples of device diagnostics are presented for RCA flip-chip mounted GaAs FET's.

Collector amplitude modulation of the class E tuned power amplifier

Abstract: In the class E high-efficiency switching-mode tuned power amplifier, the RF output amplitude is almost exactly a linear function of the collector dc supply voltage, since conduction angles and wave shapes are not changed by the dc supply voltage. Thus the RF output can be amplitude-modulated by varying the dc supply voltage in accordance with desired amplitude-modulation (AM) envelope. Deviations from the ideal linear modulation characteristic are caused by: transistor saturation voltage; RF feedthrough from the driver via C_{cb} ; nonunity transmission of the ac modulating signal into the amplifier through the nonzero inductance of the collector shuntfeed RF choke; and differences in the magnitudes and delay times, of the RF transmission function through the RF output network, of three different frequencies: lower sideband, carrier, and upper sideband. Design criteria are given, to hold the modulation distortion below a limit chosen by the designer. Experimental results agree well with analytical predictions. Distortion of the modulation envelope can easily be held below 1 percent.

Bidirectional buffer amplifier

Abstract: Bidirectional amplifier employs a single buffer amplifier (64). The bidirectional amplifier is programmed by applying a control signal (Q) and its complementary signal (Q), which establishes the state of four pass transistors (P'1, P'2, P'3, P'4) or four CMOS transmission gates (T1, T2, T3, T4). For a first selection of the control signal, the bidirectional amplifier receives an input signal on a first lead (A') and produces an amplified signal on a second lead (B'). For a second selection of the control signal, the amplifier receives an input signal on the second lead (B') and produces an amplified output signal on the first lead (A').

Power line communications terminal and interface circuit associated therewith

Abstract: A communications terminal for transmitting and receiving communication signals over a power line communications network and including an interface circuit for coupling the terminal to the power line of the network is disclosed. One embodiment of the network includes a transformer for coupling communication signals between the power line and terminal. The coupled communication signals are measured from the secondary of the transformer and used to govern an amplifier circuit which generates matched signals, representative of the measured communication signals. The matched signals are inverted in polarity at the output stage of the amplifier and applied to the secondary winding of the transformer to cancel substantially the electromagnetically coupled communication signals from the power line, thereby providing a high bridging impedance to the power line communication signals without impeding substantially the coupling of the terminal's own communication signals.

Wireless power line communication apparatus

Abstract: A field configuration terminal is provided that does not require physical or electrical connection to a remote device of a power line communication system. A toroid is provided that comprises a multiplicity of turns of a conductor that is connected in electrical communication with an amplifier and receiver circuitry within the field configuration terminal. A battery, with associated power supply components, provides a direct current source for the microprocessor and logic of the field configuration terminal and for the amplifier thereof. The toroid of the field configuration terminal is shaped to be disposed around a load management terminal of a power line communication system without physical or electrical contact therewith. Signals are transmitted to and received from the load management terminal by inductively coupling the toroid with the load management terminal in signal communication.

Gigahertz transresistance amplifiers in fine line NMOS

Abstract: Two front-end amplifiers for fiber optics applications at gigabit data rates were fabricated in fine-line NMOS. One was designed for operation at 1 Gb/s and a simpler circuit was designed for 1.7 Gb/s, with the function of amplifying a photocurrent into an output voltage. An automatic gain control (AGC) optionally follows the first amplifier. The bandwidth of the first amplifier was measured to be 920 MHz, with optical operation at 800 Mb/s at an optical sensitivity of -28 dB using a pin detector for light at 1.3 /spl mu/m wavelength. The bandwidth of the second amplifier 32 dB at a bandwidth of 870 MHz. Both circuits operated at less than their designed frequency because of discrepancies between expected and measured transconductances.

External dye-laser frequency stabilizer.

Abstract: We describe an external dye-laser frequency stabilizer that combines an acousto-optic frequency shifter with a fast electro-optic phase modulator. A compensating electronic delay line in the crossover network provides a near-ideal transducer response while keeping the voltage across the electro-optic crystal away from the amplifier limits.

Properties of the Optical Quantum Amplifier

Abstract: The properties of a linear optical amplifier or attenuator in which the input light is coupled to a collection of non-saturable atoms are considered. The photon-number factorial moments and probability distribution of the amplifier output are derived for arbitrary input statistics. Relations are obtained between the output and input variances in photon number, phase-angle cosine, and electric-field magnitude. The effects of amplification and attenuation on signal-to-noise ratio are obtained for both direct and homodyne detection. Particular attention is paid to the extents to which the non-classical properties of photon antibunching and squeezing are preserved by amplification and attenuation. It is found that both properties can at best survive only twofold intensity amplification.

Differential amplifier with rail-to-rail input capability and controlled transconductance

Abstract: A differential amplifier operable between a pair of supply voltages that define a rail-to-rail supply range contains a pair of differential portions (20 and 22) that together provide representative signal amplification across the supply range, although neither differential portion individually does so. A current control (24) regulates operating currents (IN and Ip) for the differential portions in such a way that the amplifier transconductance can be controlled in a desired manner as the common-mode part (VCM) of the amplifier input signal (VI+ and VI-) varies across the supply range. The transconductance is typically controlled to be largely constant. A summing circuit (26) selectively combines internal currents (IA, IB, IC, and ID) from the differential portions to generate at least one output signal (IO+ and IO-) representative of the input signal.

Smoke detecting apparatus

Abstract: A light sensing apparatus comprising a solid-state photocell responsive to low levels of light connected to an impedance matching buffer stage, a gain controlled amplifier stage and an output amplifier stage; a gain control network controlled by a temperature sensor for receiving an amplified signal from said output stage, the gain being adjustable to compensate for temperature dependance of the photocell signal.

Capacitive detector for transducers

Abstract: Displacement of a movable transducer element is measured by exciting a capacitive gap (preferably differential capacitive gaps) with triangular waves of voltage to obtain a square current wave output into a zero input impedance amplifier. The square wave output is amplified and synchronously detected to produce a d.c. output signal proportional to displacement. The d.c. output signal is fed back to force rebalance electrodes to electrostatically rebalance the movable transducer element. The feedback signal is a measure of the force being transduced. Initial offsets in the position of the transducer element and capacitances of the capacitive gaps are compensated by signals derived from the capacitive gap excitation waveforms.

Tuning systems on dielectric substrates

Abstract: A tuning system employs a specific resonant circuit which includes two electrodes confronting each other through a dielectric interposed therebetween. Each of the two electrodes has at least one bent portion to present a lumped-constant inductance and has a desired equivalent electrical length. The two electrodes respectively have common terminals located out of mutually confronting positions so that voltage signals induced by mutual inductance between the electrodes will be opposite in phase so as to thereby produce a parasitic distributed-constant capacitance. The two electrodes form a two-terminal circuit network having a first terminal disposed at a desired position on one of the two electrodes and the common terminals as a second terminal. The first terminal of the resonant circuit is connected to a feedback amplifier, an amplifier, or a mixer so as to form a tuning oscillator, a tuning amplifier or a mixer.

An area-efficient approach to the design of very-large time constants in switched-capacitor integrators

Abstract: A switched-capacitor integrator circuit with very high time constant using capacitive T-cells, is presented. According to a set of design equations and constraints, a test circuit previously needing an excessive capacitive ratio of over 700 has been integrated with a capacitance spread of only 25. Contrary to other designs, a simple clocking scheme is sufficient. Calculations and measurements show that in the T-cell integrator, capacitive area is conveniently traded off against amplifier specifications as open-loop and slew rate; power consumption is not necessarily compromised by these specifications. Integration of an experimental test circuit has given evidence of the ease of implementing this technique in larger systems.

Attenuation of sound waves

Abstract: An active sound control system is described in which allowance is made in a relatively uncomplicated circuit for acoustic coupling between a sound generating system for generating a cancelling sound wave and a detector for sensing a sound wave to be cancelled Unwanted sound from a source is detected by a microphone and cancelled by sound from a speaker connected by way of an amplifier to the microphone The amplifier has a feedback processing system with a transfer function which takes account of acoustic feedback between the speaker and the microphone in deriving, with the amplifier, a signal to drive the speaker

High-gain 35-GHz free-electron laser-amplifier experiment

Abstract: : A new intense-beam free-electron laser experiment, operating as a short-pulse amplifier at 35 GHz, has demonstrated linear growth rates of 12 dB/cm, total gain of 50 dB, and coherent emission of 17 MW, corresponding to an experimental efficiency of greater than 3% (Author)

Variable gain power amplifier

Abstract: A power amplifier having plural parallel amplification circuits of different gains selectively actuable to zero and maximum gains, and electronic switches to select a circuit for connection to a common output junction.

Method and system for matching the sound output of a loudspeaker to the ambient noise level

Abstract: A microphone picks up a signal in response to both the acoustic output of the speaker and the ambient noise at the loudspeaker location, for example, in an automobile The microphone output signal and the signal which is to be provided to the loudspeaker with variable amplification are each subjected to envelope detection The two envelope curve signals are compared to produce a signal representative of their similarity, the similarity being high when ambient noise is low or absent The similarity signal is then processed with reference to a reference voltage which varies with the setting of the manual volume control of the amplifier interposed ahead of the loudspeaker That amplifier has an automatic volume control input to which a control signal generated in response to the envelope similarity signal is applied to raise the amplification and the loudspeaker output level when ambient noise, detected by the similarity of the envelope signals, is present or increases The system and method have the advantage that special calibration of the system in place of use, for proper balancing of the microphone output against the useful signal is made unnecessary The envelope signal comparison is simply performed by comparing the respective signs of the slopes of the respective envelope curves to supply a first output value when the signs are identical and a second output value when they are opposite The output values are weighted by a factor dependent upon signal dynamics (derived from average value and dynamic range) to reduce the larger output value and at the same time increase the smaller one by a dynamic factor The succession of weighted output values thus produced is integrated to produce the similarity signal