Showing papers on "Amplifier published in 1990"

Microwave Circuit Design Using Linear and Nonlinear Techniques

Abstract: Foreword by David Leeson. Preface. 1. RF/Microwave Systems. 2. Lumped and Distributed Elements. 3. Active Devices. 4. Two-Port Networks. 5. Impedance Matching. 6. Microwave Filters. 7. Noise in Linear Two-Ports. 8. Small- and Large-Signal Amplifier Design. 9. Power Amplifier Design. 10. Oscillator Design. 11. Microwave Mixer Design. 12. RF Switches and Attenuators. 13. Microwave Computer-Aided Workstations foor MMIC Requirements. Appendix A: BIP: Gummel-Poon Bipolar Transistor Model. Appendix B: Level 3 MOSFET. Appendix C: Noise Parameters of GaAs MESFETs. Appendix D: Derivations for Unilateral Gain Section. Appendix E: Vector Representation of Two-Tone Intermodulation Products. Appendix F: Passive Microwave Elements. Index.

A high-swing, high-impedance MOS cascode circuit

Abstract: A simple cascode with the gate voltage of the cascode transistor being controlled by a feedback amplifier called a regulated cascode is presented. In comparison to the standard cascode circuit, the minimum output voltage is lower by about 30 to 60% while the output conductance and the feedback capacitance are lower by about 100 times. An analytical large-signal, small-signal, and noise analysis is carried out. Some applications like current mirrors and voltage amplifiers are discussed. Experimental results confirming the theory are presented. >

Amplifier linearization using a digital predistorter with fast adaptation and low memory requirements

Abstract: A method is described for linearizing a power amplifier by predistorting its input. It is particularly well suited to baseband implementation with digital signal processor hardware. In comparison with the most powerful previously published predistorter, it requires four orders of magnitude less memory, reduces convergence time by over three orders of magnitude, eliminates reconvergence time following a channel switch, and eliminates the need for a phase shifter in the feedback path. The predistorter structure is described. Its ability to suppress intermodulation products using only a small table is demonstrated. The effect of predistorter nonidealities (especially limited table size) on the power amplifier's output are analyzed. A fast adaptation algorithm is introduced. >

Nonlinear amplifying loop mirror.

Abstract: A novel device arrangement for all-optical switching that permits efficient exploitation of waveguide nonlinearities is discussed. It is based on a long optical fiber loop mirror with an integral short asymmetrically located optical amplifier. The device performance is demonstrated by using a Nd3+-doped fiber amplifier. Switching is obtained for peak signal powers of less than 1 W and an amplifier pump power of 10 mW.

Microwave circuit design using linear and nonlinear techniques

Abstract: Foreword by David Leeson. Preface. 1. RF/Microwave Systems. 2. Lumped and Distributed Elements. 3. Active Devices. 4. Two-Port Networks. 5. Impedance Matching. 6. Microwave Filters. 7. Noise in Linear Two-Ports. 8. Small- and Large-Signal Amplifier Design. 9. Power Amplifier Design. 10. Oscillator Design. 11. Microwave Mixer Design. 12. RF Switches and Attenuators. 13. Microwave Computer-Aided Workstations foor MMIC Requirements. Appendix A: BIP: Gummel-Poon Bipolar Transistor Model. Appendix B: Level 3 MOSFET. Appendix C: Noise Parameters of GaAs MESFETs. Appendix D: Derivations for Unilateral Gain Section. Appendix E: Vector Representation of Two-Tone Intermodulation Products. Appendix F: Passive Microwave Elements. Index.

High-efficiency coupling-insensitive transcutaneous power and data transmission via an inductive link

Abstract: A new approach is presented for transmitting RF power and signal via an inductive link. Such an approach optimizes the power efficiency of the overall transmission scheme comprising the power amplifier plus the inductive link. Power amplification is based on the single ended class E concept. The power amplification stage is self-oscillating, and thus the oscillation frequency is influenced by the coupling of the coils. The resulting operating frequency offset yields improved power transmission performance of the circuit, since the oscillation frequency tracks the absolute transmission efficiency maximum. A detailed analysis is given. Realization of the approach requires a minimal number of circuit components. Experimental and theoretical results are in good agreement. >

Modeling of gain in erbium-doped fiber amplifiers

Abstract: An analytic method is described for fully characterizing the gain of an erbium-doped fiber amplifier (EDFA) that is based on easily measured monochromatic absorption data. The analytic expressions presented, which involve the solution of one transcendental equation, can predict signal gains and pump absorptions in an amplifier containing an arbitrary number of pumps and signals from arbitrary directions. The gain of an amplifier was measured over a range of more than 20 dB in both pump and signal powers. The measured theoretical results agreed to within 0.5 dB. Although the results described apply explicitly to EDFAs pumped in the 1480-nm region, they are also applicable to EDFAs pumped in the 980-nm region. The method is valid whenever the gain saturation by amplified spontaneous-emission noise can be neglected, which is typically the case for amplifiers with less than about 20 dB of gain. >

Limits of low noise performance of detector readout front ends in CMOS technology

Abstract: The limits of the noise performance of detector readout front ends in CMOS technology have been studied. A theoretical minimal number of equivalent noise charge (ENC) that can be achieved by a CMOS technology is derived, taking both thermal noise and 1/f noise into account. Design criteria and techniques of CMOS readout front ends are presented so as to fully exploit the maximal capability of a CMOS technology. The optimal input transistor dimensions and bias conditions of charge sensitive amplifiers (CSA) are analytically determined. For readout front ends using semi-Gaussian pulse shapers, the optimal number of integrators and the optimal peaking time are determined from the point of view of achieving the best detector resolution. In order to verify the theoretical analyses, a charge sensitive amplifier and a fourth-order semi-Gaussian pulse shaper with 1- mu s peaking time have been designed in a standard 3- mu m CMOS technology. Calculations and computer simulations show that by optimal design of input CSA and semi-Gaussian pulse shaper, a detector resolution as low as 600 equivalent noise electrons can be obtained for a 40-pF detector capacitance. >

Optical control of microwave semiconductor devices

Abstract: The use of optically controlled devices to perform a range of circuit functions is reviewed. The optical control of amplifier performance is discussed. The optical control of two- and three-terminal oscillators and optically pumped mixers is discussed. Among the active devices treated are Gunn and IMPATT oscillators; MESFET and HEMT amplifiers, oscillators, and mixtures; and diode mixers. Future directions for research in this area are discussed. >

Frequency-hopping spread-spectrum modulation for digital communications over electrical power lines

Abstract: A solution for the precise and cost-effective generation of frequency-hopping spread-spectrum waveforms using digital frequency synthesis based on read-only-memories (ROM, PROM, EPROM) is studied. For matched filter reception of frequency-hopping spread-spectrum waveforms a new approach based on lock-in amplifiers combined with synchronous voltage controlled oscillators (SVCO) brought remarkable results in practical field tests. An application-specific digital signal processor for receiver operation in form of a CMOS gate array was also designed. Prototypes according to two different system concepts were built, and measurements of bit error probability were carried out on indoor and outdoor power-line networks. Computer simulations based on channel analysis to predict bit error probability are proposed and compared with measured results. Indoor prototypes are designed for a data rate of 300 b/s and a frequency-hop rate of 900 s/sup -1/ with a transmission voltage approximately=0.35 V/sub rms/ in a spectral range from 30 to 146 kHz. Outdoor prototypes are intended for remote meter reading featuring a data rate of 60 b/s and a frequency-hop rate of 300 s/sup -1/. Transmission voltage is variable from 0.35 to 1 V/sub rms/ in a spectral range from 30 to 146 kHz. >

A 10‐GHz frequency‐domain fluorometer

Abstract: We describe the design and performance of a 10‐GHz harmonic‐content frequency‐domain fluorometer. The modulated excitation is provided by the harmonic content of a train of ps pulses. High‐speed and/or high‐frequency detection was attained with a triode‐type microchannel plate photomultiplier tube (MCP PMT) from Hamamatsu, R‐2566‐6, with 6 μm channels. To minimize the cost of the electronic components, and to minimize the noise due to these components, the detection circuits consists of two frequency ranges, 10 MHz–2 GHz and 2–10 GHz. The upper frequency limit of 10 GHz is determined by the current MCP PMT, so the usual configuration includes a low‐noise 2–10‐GHz amplifier. This amplifier is easily replaced with a 2–18‐GHz amplifier to allow operation to 18 GHz and the use of faster PMTs, should they become available in the future. Measurement of known optical delays demonstrates the accuracy of the instrument. For instance, a 1.69 ps optical delay was measured as 1.7±0.4 ps from 0.5 to 10 GHz, and 1.7±0.2 ps from 2 to 8 GHz, where the uncertainty indicates the maximum deviation from the expected value. The data were shown to be free of systematic errors by measurements on fluorophores with single exponential decays, with decay times ranging from 61 ps to 1.24 ns. Measurement of anisotropy decays with correlation times of 24 ps are shown and it is predicted that correlation times as short as 1 ps could be measured with this instrument. And finally, the sensitivity of the instrumentation was demonstrated by measurements of the very weak intrinsic tryptophan emission of deoxyhemoglobin, which displays decay times ranging from 2 to 820 ps.

Predistorter for linearization of electronic and optical signals

Abstract: An electronic circuit provides a linear output from an amplitude modulated transmission device such as an amplifier or a semiconductor laser which has inherent distortion. The distortion of the nonlinear device is compensated by applying a predistorted signal with distortion equal in magnitude and opposite in sign to the distortion introduced by the nonlinear device. The input signal is split into two paths with the primary part of the signal applied directly to the device, with a time delay to compensate for delays in the secondary path. The secondary path generates predistortion which is recombined with the primary signal in proper phase and amplitude for cancelling distortion in the output device. A distortion generator in the secondary path generates adjustable amplitude intermodulation signals. Filtering is used before the distortion generator to compensate for the dependence of the distortion of the nonlinear device on the frequencies of the fundamental signals. Filtering is used after the distortion generator to compensate for the dependence of the distortion of the nonlinear device on the frequency of the distortion. Phase of the distortion signal is adjusted to be in proper phase relation with the distortion of the device. Set points of the predistorter may be adjusted automatically. More than one secondary path may be used.

Erbium-doped fiber amplifier

Abstract: This invention is a rare earth doped optical amplifier with increased gain and lowered pump thresholds. The amplifying scheme is based on a 3 level lasing system rather than the more prevalent 4 level lasing system. Additionally, the transmission mode of the optical fiber at the pump wavelength has a radius which is substantially equal to or greater than the radius of the distribution profile of the rare earth ions in the fiber amplifier core. With the inventive amplifier, a gain of 37 dB and a saturation power of 11.3 dBm has been obtained with only 54 mW of launch power at λ=1.49 μm.

Femtosecond gain dynamics in InGaAsP optical amplifiers

Abstract: We have studied ultrafast gain dynamics in InGaAsP optical amplifiers by means of pump‐probe and cross‐correlation measurements using 180 fs optical pulses. The data show strong gain nonlinearities due to nonequilibrium carrier distributions and differ significantly from those observed in AlGaAs amplifiers.

A 10-b 15-MHz CMOS recycling two-step A/D converter

Abstract: A two-step recycling technique is applied to implement a 10-b CMOS analog-to-digital (A/D) converter with a video conversion rate of 15 Msample/s. In a prototype digitally corrected converter, one capacitor-array multiplying digital-to-analog converter (MDAC) is used repeatedly as a sample-and-hold (S/H) amplifier, a DAC, and a residue amplifier so that the proposed converter may obtain linearity with the capacitor-array matching. An experimental fully differential A/D converter implemented using a double-poly 1- mu m CMOS technology consumes 250 mW with a 5-V single supply, and its active die area, including all digital logic and output buffers, is 1.75 mm/sup 2/ (2700 mil/sup 2/). Because the conversion accuracy of the proposed architecture relies on a capacitor-array MDAC linearity, high-resolution CMOS A/D conversions are feasible at high frequencies if sophisticated circuit techniques are further developed. For high-speed two-phase versions, the system can be easily modified to use multiplexing and/or pipelining techniques with a separate S/H amplifier and/or two separate flash converters. >

Raster scan control system for a charged-particle beam

Abstract: A raster scan control system (18) for use with a charged-particle beam delivery system (20) provides precise control of large currents driving an inductive load. The beam delivery system includes a nozzle through which a charged-particle beam (24), such as a proton beam, passes prior to being directed to a target (32). The nozzle includes both fast and slow sweep scan electromagnets (204, 208) that cooperate to generate a sweeping magnetic field that steers the beam along a desired raster scan pattern at the target. The electromagnets are driven by large currents (213, 215) from the raster scan control system. The raster scan control system includes both fast and slow power amplifiers (212, 214) for delivering the desired large currents to the fast and slow electromagnets, respectively; monitoring means (206, 210) for monitoring the magnetic fields; sensing means (212, 230) for sensing the large currents; feedback means for maintaining the magnetic fields and large current at desired levels; out of tolerance means for automatically causing the servo power amplifiers to steer the beam away from the target area in the event the error signal becomes excessive; a programmable raster generator (80) for providing the fast and slow power amplifiers with a raster scan signal (216, 218) that defines the desired raster pattern; and a power supply (74) for delivering the requisite power to the power amplifiers and other components.

High frequency surgery device for cutting and/or coagulating biologic tissue

Abstract: A high frequency AC electro-surgery apparatus is equipped with an automatic regulation loop for controlling the output voltage (Ua) rather than the output power. An electrically isolating coupling in the form of an isolation transformer (5) is followed by a voltage converter (6) to provide DC voltage signal (a) proportional to a measure of the high frequency AC output voltage (Ua). The DC voltage signal (a) is supplied to a regulating amplifier (7) to which a reference voltage signal (b) is supplied by a reference voltage source (8), to produce an output signal (c) that is furnished to the control input of an electronically controlled power supply (16). The latter controls the operating voltage (Ub) for the amplifier (2) of the high frequency AC generator in such a manner that the output AC voltage (Ua) at the output terminals (10, 11) corresponds to a desired value set by the reference voltage signal (b).

Pulsed twin beams of light

Abstract: Pulsed twin beams of light have been generated using an optical-parametric amplifier that is pumped by the second harmonic of a mode-locked and Q-switched neodymium:yttrium aluminum garnet laser. The intensity noise levels on the direct-detected signal and idler beams are found to be correlated by more than 15 dB, and the subtracted noise falls below the quantum limit by more than 6 dB (75%). To our knowledge, this is the first observation of pulsed twin beams of light, and yields the highest quantum-noise reduction observed in any experiment to date. Our measurements are in excellent agreement with the quantum theory of a nondegenerate optical-parametric amplifier.

Pump source requirements for end-pumped lasers

Abstract: A simple model is developed to relate laser design and properties of a gain medium to the requirements on a pump source for end-pumped lasers or amplifiers. A novel technique for scaling the pump power or energy for end-pumped lasers is presented and analyzed in terms of this model. The results indicate that power or energy scaling of the pump source for end-pumped lasers is not limited by geometry; however, the results also show that some minimum pump energy or power is required. >

CMOS amplifier with offset adaptation

Abstract: An integrated circuit amplifier having a random input offset voltage is adaptable such that the input offset voltage may be cancelled out. An inverting input node is a floating input node and is coupled to a source of input signal by a first capacitor. A second capacitor is connected between the output of the amplifier and the floating node. An ultraviolet window above the second capacitor allows the floating node to be charged, by the application of ultraviolet light, to a voltage which effectively cancels the input offset voltage. The ultraviolet window and capacitor electrodes are arranged such that the ultraviolet light may strike only the desired areas of the structure.

Amplex, a low-noise, low-power analog CMOS signal processor for multi-element silicon particle detectors

Abstract: AMPLEX is a monolithic analog signal processor fabricated in 3 μm n-well CMOS and originally designed for the inner silicon detector of the UA2 Experiment at the CERN SPS Collider. However, it is suitable for various other types of detectors, and results are also given for a multiwire proportional chamber (MWPC). The chip contains 16 channels, each consisting of a charge amplifier, a shaper amplifier and a track-and-hold stage. The channel outputs are connected to an analog multiplexer which is controlled by digital circuitry. For a power consumption of 1 mW per channel and an adjustable peaking time of 600 to 800 ns, the equivalent noise charge is 400 rms electrons plus 33 rms electrons per pF of input capacitance. The DC stabilisation of the charge amplifier is obtained using a non-linear feedback resistor. This novel MOS element is a key feature of the design and enables low noise as well as DC stability of the charge amplifier, even for increased detector leakage current up to several hundred nA. Such operating conditions can occur following radiation damage of silicon pad detectors.

Considerations for fast settling operational amplifiers

Abstract: The design considerations for fast-settling operational amplifiers (op amps) are significantly different between sampled-data switched-capacitor (SC) and conventional continuous-time applications. In SC circuits, the shape of the output voltage waveform of an op amp is of no consequence provided that the output settles to within a specified tolerance of its steady-state value prior to the next sampling instant. This feature allows for an optimum op amp frequency shaping to obtain a minimum small-signal settling time. The theory applies to any op amp that is well approximated by a two-pole model, including the conventional two-stage and single-stage folded-cascode topologies. As the commonly used equivalent-circuit Miller-effect model for frequency compensation has generally been improperly applied to two-stage transconductance amplifiers, it does not provide sufficient accuracy to achieve the optimum phase margin condition. Therefore, the use of equivalent-circuit models has been refined to provide greater accuracy and to eliminate some previous misconceptions. >

On the design of voltage-controlled sinusoidal oscillators using OTAs

Abstract: A unified systematic approach to the design of voltage-controlled oscillators using only operational transconductance amplifiers (OTAs) and capacitors is discussed. Two classical oscillator models, i.e. quadrature and bandpass-based, are employed to generate several oscillator structures. They are very appropriate for silicon monolithic implementations. The resulting oscillation frequencies are proportional to the transconductance of the OTA, and this makes the structures well-suited for building voltage controlled oscillators (VCOs). Amplitude stabilization circuits using both automatic gain control (AGC) mechanisms and limitation schemes are presented. The circuits are compatible with the transconductance amplifier capacitor oscillator (TACO). Experimental results from bipolar breadboard and CMOS IC prototypes showing the potential of OTA-based oscillators for high-frequency VCO operation are included. >

A monolithic 20 b delta-sigma A/D converter

Abstract: Oversampled delta-sigma converters have been used for high-resolution analog-to-digital conversion over a wide range of input frequencies. Oversampled converters reduce the need for complex antialias filters, eliminate sample-and-hold amplifiers, and are free of differential nonlinearity errors. A fourth-order converter with a dynamic range of 123 dB and a signal-to-total-harmonic-distortion ratio of 126 dB is described. The input voltage range is 20 V peak to peak, the input signal bandwidth is DC to 500 Hz, the clock frequency is 1024 MHz, and the output word rate is 32 K/s. The 4.48*6.53-mm chip is packaged in a 28-pin plastic leaded chip carrier/leadless chip carrier (PLCC/LCC) and dissipates 120 mW using +5 V, -5 V, and ground. >

Interface circuits including driver circuits with switching noise reduction

Abstract: An interface circuit includes a generator for driving an interface signal to a receiver which produces an output signal in response thereto. The generator (or driver) includes a pair of relatively larger complementary conductivity field effect transistors and a pair of relatively smaller complementary conductivity field effect transistors (FETs), each pair in series circuit between the supply rails. The interface signal is produced at a connection of the center points of both pairs of FETs. A control device renders like ones of the FETs in each pair alternately conductive responsive to the input signal, however, the control device generates control signals for the FETs such that the relatively smaller FET of a given conductivity becomes conductive before the larger FET of that same conductivity. The receiver includes a voltage divider to attenuating and coupling the received interface signal to a high-gain amplifier which produces the output signal. Preferably, the signals have amplitudes sufficiently large to cause the interface circuit to operate as a digital interface. Further, it is preferred that two generators of opposite signal sense be employed to produce a differential interface signal, in which case the receiver includes a differential amplifier having opposite signal sense inputs to which the differential signals are applied through a differential voltage divider. In the preferred differential amplifier, opposite signal sense outputs are fed back in the regenerative sense to the two inputs to introduce hysteresis.

Radio telephone using received signal strength in controlling transmission power

Abstract: A radio telephone uses a signal indicating the strength of received communication signals as a measure of prevailing signal propagation conditions to control the gain of a power amplifier in its transmitter. Where conditions are favorable, the gain can be reduced without deleterious effects on transmitted signals, and with a resulting savings in power drain on the radio telephone's power supply (e.g., batteries). In this way, talktime on a single battery charge can be significantly lengthened. Where conditions are adverse, e.g., at outlying or fringe areas of a cellular telephone system of which the radio telephone is a station, the gain can be increased to produce stronger transmitted signals, at times extending the effective coverage area of such systems. Preferably, the output of the power amplifier remains at all times within a power range prescribed by applicable standards, and is increased or decreased within the power range in accordance with prevailing conditions indicated by the received signal strength signal.

Characterizing the effects of nonlinear amplifiers on linear modulation for digital portable radio communications

Abstract: The design and performance of linear modulation techniques and RF power amplifiers are discussed Various types of power amplifier are used in the comparison, using simulation, of out-of-band radiation and power efficiency The designs focus on high-frequency silicon bipolar power amplifiers suitable for low-power portable radio applications Two different 4-QAM (4-level quadrature amplitude modulation) schemes are compared Power efficiency as high as 40% can be achieved using a dynamically biased amplifier operating near saturation The effects of nonlinear distortions from power amplifiers on adjacent channel interference as well as bit and block error rate performance are also investigated >

Theory of hot carrier effects on nonlinear gain in GaAs-GaAlAs lasers and amplifiers

Abstract: A concise and straightforward model of nonlinear grain based on the carrier heating effect in semiconductor lasers is presented. The problem is formulated using the density matrix approach and includes a priori the effect of free-carrier absorption. Coupled field-medium equations involving photon densities, carrier densities, and carrier temperatures are derived using the results of the density matrix method. The propagation of ultrashort pulses in laser amplifiers is studied and a qualitatively new model along with results on the transient gain recovery dynamics are presented. The model accounts for the wavelength dependence of the asymmetric part of the nonlinear gain observed in direct mixing experiments observed in semiconductor lasers. >

A CMOS large-swing low-distortion three-stage class AB power amplifier

Abstract: A CMOS power amplifier with a class AB rail-to-rail output stage is presented. By using a three-stage amplifier with double Miller compensation, the harmonic distortion of the output stage is suppressed by the internal feedback loops. This approach is thoroughly investigated, and it is shown that a three-stage amplifier has apparent advantages for DC gain, harmonic distortion, and power-supply rejection ratio (PSRR). A realized prototype for ISDN applications with a gain bandwidth (GBW) of 5 MHz and with -80-dB THD at 10 kHz for an output current of 20 mA in a load of 81 Omega is presented. >

Parallel amplifiers with combining phase controlled from combiner difference port

Abstract: A power amplifier arrangement includes a power divider for dividing the signal to be amplified into equal-amplitude components Each component is amplified by a signal amplifying path The amplified signals are applied to a phase-sensitive power combiner The combined signal appears at the sum port and a phase-related difference signal appears at a difference port of the combiner The difference signal is processed to produce a control signal for controlling the relative phases of the signals passing through the signal amplifying paths