Search

We introduce a class of topological lasers based on the photonic Floquet topological insulator concept. The proposed system is realized as a truncated array of the lasing helical waveguides, where the pseudo-magnetic field arises due to twisting of the waveguides along the propagation direction that breaks the time-reversal symmetry and opens up a topological gap. When sufficient gain is provided in the edge channels of the array then the system lases into the topological edge states. Topological lasing is stable only in certain intervals of the Bloch momenta, that ensure a dynamic, but stable balance between the linear amplification and nonlinear absorption leading to the formation of the breathing edge states. We also illustrate topological robustness of the edge currents by simulating lattice defects and triangular arrangements of the waveguides., 23 pages, 5 figures

How to realize the detection of tiny birefringence is an important but challenging issue for investigations and applications in optics. In weak measurements, weak-value amplification has been widely applied to the precise estimation of time delay. Here, we show that the linear amplification in weak measurements has the potential to outperform standard weak-value amplification for ultra-small parameter characterization. The higher measurement accuracy in the linear amplification enables us to achieve a measurement of stress-induced birefringence with a high resolution of 5 × 10 − 10. Compared with existing methods, the accuracy based on weak measurements for birefringence detection can improve two orders of magnitude. Our method may have important applications in a variety of fields involving the precise measurement of time delay or birefringence.

Background Non-invasive prenatal testing (NIPT) as alternative screening method had been proven to have very high sensitivity and specificity for detecting common aneuploidies such as T21, T18, and T13, with low false positive and false negative rates. Unfortunately, recent studies suggested that the NIPT achieved lower accuracy in sex chromosomal aneuploidies (SCAs) detection than autosomal aneuploidies detection. BGISEQ-500 powered by Combinatorial Probe-Anchor Synthesis (CPAS) and DNA Nanoballs (DNBs) technology that combined linear amplification and rolling circle replication to reduce the error rate while enhancing the signal. Therefore, NIPT based on CPAS might be a good method for SCAs screening in routine clinical practice. In the study, we intended to evaluate the clinical utility of NIPT based on CPAS on screening for fetal SCAs. Results A total of 570 pregnant women were included in the retrospective study. Maternal blood samples were collected for NIPT; amniocentesis was performed on all pregnant women. NIPT was carried out by BGISEQ-500 sequencing platform based on CPAS. Karyotype analysis of amniotic cells was performed by standard G-banding techniques. 43 out of the total 570 pregnant women tested by NIPT showed fetal SCAs (19 of 45,X, 12 of 47,XXY, 10 of 47,XXX, and 2 of 47,XYY). The following amniocentesis confirmed that 26 cases were true positive (7 of true positive 45,X, 9 of true positive 47,XXY, 9 of true positive 47,XXX as well as 1 of 47,XYY) and the positive predictive value (PPV) for fetal SCAs was 60.47%. In addition, the PPV of advanced maternal age group (67.74%) was higher than the other indications group (45.45%) or serological screening high-risk /critical-risk group (0%). Conclusions NIPT based on CPAS could be a potential method for SCAs screening. However, it still had high false positive rates, especially for 45,X. The pregnant women with fetal SCAs detected by NIPT, especially those with non-age-related prenatal diagnostic indications, should be advised to accept invasive prenatal karyotype analysis.

The most important property of the Doherty amplifier is the load modulation, which carries out the perfect combining of the asymmetrical powers from the two amplifiers. Thereby, only one amplifier (called carrier amplifier) operates at a low power level, and the two amplifiers (the second one is called peaking amplifier) generate powers at a higher power level. Also the carrier amplifier operates at the peak efficiency mode, while the peaking amplifier is operational due to the nice load modulation characteristic. Another important characteristic of the Doherty load modulation is that the overall gain of the amplifier is constant, providing a linear amplification. The Doherty circuit can modulate the real part of impedance only. To get the proper load modulation for a device with a complex impedance, an offset line is needed to provide the imaginary impedance transformation. The load modulation principle and the offset line operation are discussed. Several load modulation methods are also described.

We present CPA-free linear amplification of 6:3 ps pulses in Ho:YLF crystals up to 100 μJ pulse energy at 10 kHz repetition rate. The seed pulses at a wavelength of 2:05 μm are provided by a Ho-based all-fiber system consisting of a soliton oscillator and a subsequent pre-amplifier followed by a free-space AOM as pulse-picker. Considering the achieved pulse peak power at MW-level, this system is a powerful tool for efficient pumping of parametric amplifiers addressing the highly demanded mid-IR spectral region. In detailed numerical simulations we verified our experimental results and discuss scaling options for pulse duration and energy. © 2018 SPIE.

A horn-waveguide reflective semiconductor optical amplifier was studied. Experimental results reveal that it has an excellent saturation effect for the downstream signal and linear amplification for the upstream signal compared to the straight design.

We study non-Hermitian photonic lattices that exhibit competition between conservative and non-Hermitian (gain/loss) couplings. A bipartite sublattice symmetry enforces the existence of non-Hermitian flat bands, which are typically embedded in an auxiliary dispersive band and give rise to non-diffracting "compact localized states". Band crossings take the form of non-Hermitian degeneracies known as exceptional points. Excitations of the lattice can produce either diffracting or amplifying behaviors. If the non-Hermitian coupling is fine-tuned to generate an effective $\pi$ flux, the lattice spectrum becomes completely flat, a non-Hermitian analogue of Aharonov-Bohm caging in which the magnetic field is replaced by balanced gain and loss. When the effective flux is zero, the non-Hermitian band crossing points give rise to asymmetric diffraction and anomalous linear amplification., Comment: Revised manuscript. 8 pages, 5 figures

Purpose – The purpose of this paper is to present the design of a microgripper system that comprises a dual jaw actuation mechanism with contact sensing. Design/methodology/approach – Interdigitated lateral comb-drive-based electrostatic actuator is used to move the gripper arms. Simultaneous contact sensing of the gripper jaws has been achieved through transverse comb-based capacitive sensor. The fabricated microgripper produces a displacement of 16 μm at gripper jaws for an applied actuation voltage of 45 V. Findings – It is observed that the microgripper fails to operate for the maximum performance limits (70 μm jaws displacement) and produces uncontrolled force at the tip of the jaws > 45 V. Originality/value – A novel behavioral model of the microgripper system is proposed using the fabricated dimensions of the system to carry out a detailed analysis to understand the cause of this failure. The failure analysis shows that the microgripper system failed to operate in its designed limits due to the presence of side instability in the designed combs structure. Our proposed failure model helps in redesigning the actuator to ensure its operation above 45 V so that the gripper jaw can be displaced to its maximum limit of 70 μm and also result in the increase of the controlled force from 250 to 303 μN at the microgripper jaws.

We introduce a weakly coupled photonic crystal waveguide as a promising and realistic model for all-optical amplification. A symmetric pillar type coupled photonic crystal waveguide consisting of dielectric rods periodically distributed in a free space is proposed as all-optical amplifier. Using, the unique features of the photonic crystals to control and guide the light, we have properly chosen the frequency at which only one mode (odd mode) becomes the propagating mode in the coupled photonic crystal waveguide, whereas another mode (even mode) is completely reflected from the guiding structure. Under this condition, the all-optical amplification is fully realized. The amplification coefficient for the continuous signal and the Gaussian pulse is calculated.

A modified linear amplification with nonlinear component (LINC) transmitter is presented using a novel power combination scheme.By using multiple LINC sections in parallel with a compact adaptive power combining network, the output power of power amplifiers can be boosted, together with obtaining higher efficiency over a large power back-off region. Compared to existing designs, no gate bias adaptation is needed and efficiency can be further improved. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26086

In this paper, we analyse the effect of the path imbalances(gain and phase mismatches) in LINC(LInear amplification with Nonlinear Component) system, and propose a simple scheme using LUTs(Look Up Table) to compensate the path imbalances. The EVM(Error Vector Magnitude) and ACPR(Adjacent Channel Power Ratio) of the LINC system are degraded significantly by the path imbalances because it adopts an outphasing technique. The EVM and ACPR are theoretically extracted for two variables(gain and phase mismatch factors) and 2-D LUTs for those are generated based on the analysis. The efficient and simple compensation scheme for the path imbalances is proposed using the 2-D LUTs. A LINC system with the suggested compensation scheme is implemented, and the proposed method is verified with an experiment. A 16-QAM signal with 1.5 MHz bandwidth is used. Before the compensation, the path gain ratio was 95 % and phase error was . The proposed scheme adjusts those values with 99 % and , and improves ACPR about 18.1 dB.

In this article, we propose a new impedance match method in serial Chireix combiner to improve the efficiency of Linear amplification with Nonlinear Components (LINC) amplifier. Based on the impedance characteristics of the serial Chireix combiner, two transmission lines are added between power amplifiers (PAs) and Chireix combiner in LINC. For experimental verification, the PAs and combiner are implemented and tested. From the measured results, this method is proved available for improving efficiency of LINC, and convenient for design as well as tuning work. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1418–1421, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25205

In this letter, an active metamaterial sample embedded with miniature monolithic microwave amplifiers is designed, experimentally realized, and measured. Experiments show that by proper design and direct current (DC) bias, the metamaterial sample provides almost linear amplification to an electromagnetic incidence, which can be used to compensate the loss inherent in traditional passive metamaterial and magnify the signal entered the metamaterial. This property would have important potentials in promoting the further researches of metamaterial-based applications. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 92–95, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24871

This study aimed to determine the low- and high-frequency compression ratios of a fast-acting device that were preferred by people with moderately severe to profound hearing loss. Three compression ratios (1:1, 1.8:1, and 3:1) were combined in the low and high frequencies to produce nine schemes that were evaluated pair-wise for three weeks in the field using an adaptive procedure. The evaluation was performed by 21 experienced hearing aid users with a moderately severe to profound hearing loss. Diaries and an exit interview were used to monitor preferences. Generally, the subjects preferred lower compression ratios than are typically prescribed, especially in the low frequencies. Specifically, 11 subjects preferred linear amplification in the low frequencies, and 14 subjects preferred more compression in the high than in the low frequencies. Preferences could not be predicted from audiometric data, onset of loss, or past experience with amplification. The data suggest that clients with moderately severe to profound hearing loss should be fitted with low-frequency compression ratios in the range 1:1 to 2:1 and that fine-tuning is essential. Este estudio trató de determinar las tasas de compresión de alta y baja frecuencia de un dispositivo de acción rápida, que resultara preferido por personas con hipoacusias moderadamente severas a profundas. Se combinaron tres tasas de compresión (1:1, 1.8:1, y 3:1) en las frecuencias graves y agudas para producir nueve esquemas que fueron evaluados en el campo, en pares, durante tres semanas, utilizando un procedimiento de adaptación. La evaluación fue realizada por 21 usuarios experimentados de audífono con hipoacusias moderadamente severas a profundas. Se usaron diarios y un cuestionario final para monitorear las preferencias. Generalmente, los sujetos prefirieron menores tasas de compresión de lo que típicamente se prescribe, especialmente en las bajas frecuencias. Específicamente, 11 sujetos prefirieron la amplificación lineal en las frecuencias graves y 14 sujetos prefirieron más compresión en las frecuencias altas. Las preferencias no podían predecirse a partir de los datos audiométricos, del inicio de la pérdida, o por experiencias anteriores con amplificación. Los datos sugieren que los clientes con hipoacusias moderadamente severas a profundas, deberían adaptarse con tasas de compresión en las frecuencias graves en el rango de 1:1 a 2:1, y que un ajuste fino es esencial.

Various hydraulic test and numerical simulations have reported that under the condition in which doublerow bars initially form, the mode of bars is reduced and alternate bars are formed over time. In this study, weakly nonlinear analysis is performed in order to elucidate the interaction between the modes of double-row bars and alternate bars. A concept of the rate of linear amplification is introduced in to the weakly nonlinear analysis in order to enable a consistent expansion of alternate bars and double-row bars. This analysis succeeds in reproducing the characteristics of bar mode decrease process. According to this analysis, neither of both modes (alternate bars and double-row bars ) can grow up simultaneously.

A systematic synthesis process is described for the simulation of current-controllable FDNRs using linear transcapacitance amplifiers. The process is used to obtain three circuits; two are believed to be novel. The values of the FDNRs are controllable by adjusting the bias currents of the transcapacitance amplifiers. In order to implement the obtained FDNRs, a new transcapacitance amplifier is designed. Operation principles of designed circuits are presented and experimental results are used to verify theoretical predictions. The results show close agreement between predicted behaviour and experimental performance.

We conduct a thorough comparison of two basic notch filters employed to mitigate the pattern effect that manifests when semiconductor optical amplifiers (SOAs) serve linear amplification purposes. The filters are implemented using as the building architecture the optical delay interferometer (ODI) and the microring resonator (MRR). We formulate and follow a rational procedure, which involves identifying and applying the appropriate conditions for the filters’ spectral response slope related to the SOA pattern effect suppression mechanism. We thus extract the values of the free spectral range and detuning of each filter, which allow one to equivocally realize the pursued comparison. We define suitable performance metrics and obtain simulation results for each filter. The quantitative comparison reveals that most employed metrics are better with the MRR than with the ODI. Although the difference in performance is small, it is sufficient to justify considering also using the MRR for the intended purpose. Finally, we concisely discuss practical implementation issues of these notch filters and further make a qualitative comparison between them in terms of their inherent advantages and disadvantages. This discussion reveals that each scheme has distinct features that render it appropriate for supporting SOA direct signal amplification applications with a suppressed pattern effect.

This paper presents a new correction technique for linear amplification with nonlinear component transmitters. During the transmit mode, the algorithm modulates and filters the baseband signal as a normal signal component separator, while during the correction mode, by use of a downconversion mixer, the gain and phase imbalance are measured and compensated by introducing a correction. This system is free of adjacent channel interference during the correction period. Analytical results and simulations demonstrate that this system is sufficient to suppress the out-of-band spectrum for mobile communications.

In the years before 1947, many, if not most, engineers had the idea that it was physically impossible for a solid to amplify electrical signals. After Bell Labs demonstrated that this idea was wrong, how would engineers and managers go about bringing the new amplifying device up to the level of usability of the vacuum tube? How would its unique characteristics be exploited? How would we convince the armed forces that this device could meet their demanding applications? Why did the early transistors lend themselves well to computing circuits and lend themselves poorly to linear amplification? What was the origin of practices such as temperature cycling and burn-in that became widespread in later years? How did Astounding Science Fiction Magazine play a role? How was information exchanged with universities and government organizations? How were project managers chosen and how did they manage? Some of the answers are found in these memoirs recalling J.A. Morton's Signal Corps project and J.H. Felker's TRADIC Phase I computer project.

After they first appeared on the scene in the early 1900s [1], a series of improvements on vacuum tubes occurred in the second decade of the 20th century, leading them to maturity. A major advancement was introduced by an American chemist and physicist Irving Langmuir (18811957) of the GE Research Laboratory in 1912, who used his new mercury vapor diffusion pump to obtain high vacuum tubes. These proved much more durable, reliable, and capable of linear amplification at high frequencies, thus opening the way to their wider application. Langmuir, who obtained his doctorate under Nobel laureate Walther Nernst in Gottingen, Germany, (perfecting in Europe was a common practice among talented American researchers of the time: top scientists Joshia W. Gibbs and Henry A. Rowlands did the same) was the first to explain the theory of the device and developed it into a tube dubbed Pliotron (De Forest, the inventor of Audion, erroneously thought that residual gas was essential for its conduction). After introducing inert-gas filling of incandescent bulbs in 1913, thus greatly lengthening their lifetime and assuring huge incomes for GE, he was let free to follow his research interests in surface chemistry, which ultimately led him to the Nobel Prize in 1932, the first awarded to an industrial chemist.

We review the recent developments of GaInP/GaAs heterojunction bipolar transistors (HBTs) used for microwave power, low noise, linear amplification and high temperature applications. Special attention is paid in the comparison of the GaInP HBT results with the more conventional AlGaAs HBTs. The material and processing advantages, as well as the electronic and thermal properties of GaInP are described.

Previous studies of the phase properties of optical linear amplifiers and attenuators have been restricted to situations where the effect on the phase of single-mode light is found to be diffusive. In this paper we give an analysis of phase-sensitive linear amplification and attenuation in the weak-field regime that clearly reveals a non-diffusive effect on the phase. Indeed we show that a weak field which has initially a uniform phase probability density can inherit non-random phase properties from both phase-sensitive attenuators and amplifiers. In contrast, we find that phase-insensitive amplifiers and attenuators have merely a diffusive effect on the phase of the light.

In this paper, we propose a simple relaying protocol, namely clip-amplify-forward (CAF), for dual-hop transmissions. In the CAF relaying protocol, the received signal at the relay node is clipped firstly and then amplified with a fixed amplification gain before retransmission. Only a hard clipper and a linear amplifier are needed at the relay node, where no channel estimation is needed. Simulation results show that with a relatively small amplification gain, the CAF relaying protocol has very close performance to the AF relaying protocol while enjoying the simplicity of implementation. A simple design criterion for the amplification gain is also presented.

This study assessed the efficacy of an adaptive frequency response hearing aid (AFR) for improving speech perception ability in noise among a group of elderly hearing-impaired listeners. A speech recognition task, self-assessed speech intelligibility task, and qualitative judgment task were administered to examine subtle differences in the effects of the AFR "signal processing" versus linear amplification. Group scores showed statistically significant improvement with AFR processing on the speech recognition task involving high-predictability sentences, but not on any other measures. However, there was a trend toward improved scores with AFR processing for low-predictability sentences as well. These results suggest that AFR circuitry may be most useful for enhancing recognition of speech in high-cue contexts. Wide individual subject variability was observed on all measures. This demonstrates the importance of evaluating the effectiveness of noise reduction hearing aids on an individual basis and with more than one task.

A novel power conversion mode is structured by hybridizing switch power conversion mode with linear amplification mode, so as to acquire their synthetic optimal performances. The theoretical analyses and experimental results are presented in this paper. It is proved that the novel converters can match multi-kind of loads (including nonlinear loads) with strong robustness, good waveforms and high efficiency. Its application prospect can be expected, particularly for the conditions where serious static and dynamic performances are required. Simulation and experimental result show the truth of Switch Linear Hybrid power converter.

Acclimatization was studied in hearing-impaired patients with no previous hearing aid (HA) experience who were fit bilaterally with either wide dynamic range multichannel compression (WDRMCC) or linear amplification (LA) HAs. Throughout 40 weeks of normal HA use, we monitored changes in nonsense syllable perception in speech-spectrum noise. Syllable recognition for WDRMCC users improved by 4.6% over the first 8 weeks, but the 2.2% improvement for LA users was complete in 2 to 4 weeks. Consonant confusion analyses indicated that WDRMCC experience facilitated consonant identification, while LA users primarily changed their response biases. Furthermore, WDRMCC users showed greater improvement for aided than unaided stimuli, while LA users did not. These results demonstrate acclimatization in new users of WDRMCC HAs but not in new users of LA HAs. A switch in amplification type after 32 weeks produced minimal performance change. Thus, acclimatization depended on the type of amplification and the previous amplification experience.

An outphasing system at 2.14 GHz using LDMOS power amplifiers with an attempt to use composite right/left handed material transmission (CRLH) lines in the combiner part is presented. Linear amplification using nonlinear components (LINC) is a method that improves linearity without cost in Power Efficiency. By summing two constant-envelope phase modulated signals this system exhibits high efficiency performance since the amplifiers used can be operated close to saturation levels and still get reasonably linear output.

A hybrid circuit, integrated in a double-stage microwave amplifier, able to compensate for gain variations in the -54-75/spl deg/C temperature range and 6-18 GHz frequency band, has been designed, realized, and measured. Analytical studies show that cascode configuration for the amplifiers is the best one to solve the problem. Measured results are In good agreement with the analysis.

This paper describes guidelines for designing thin-film SOI power MOSFETs for linear-amplification applications. The linear-amplification characteristics and DC performance depend on the grand interconnection pattern. We prefer to put the grand pattern on the drain (output) side. There are optimum finger lengths which provide the best linear amplification characteristics. Finger length also depends on the operating frequency and total gate width.

A highly efficient RF thin-film SOI power MOSFET having a self-aligned offset gate structure is proposed. It was fabricated using a self-aligned offset gate structure based on an LDD structure to reduce the on-resistance and thus increase the power-added efficiency. The target breakdown voltage was 10 V, and the fabricated device has a breakdown voltage of 14.3 V. The RF performances of the proposed power MOSFET are the acceptable for both the 2 and 5 GHz-bands. The linear amplification characteristics of the SOI power MOSFET are almost the same as those of compound semiconductor devices.

This paper describes guidelines for designing thinfilm SOI power MOSFETs for linear-amplification and SPDT-switch applications. A fabricated device shows power-added efficiency of 61% at 5.25 GHz (Vdd @ 3.0 V). For linear-amplification, it is important to suppress the parasitic bipolar effect and reduce the on-resistance. For a SPDT-switch, it is important to reduce Ron and use highresistivity Si substrate.

In low k1 optical-lithography generation, there is a non- linear amplification of mask critical dimension (CD) error during image transferring on a wafer. This error factor is called mask error enhancement factor (MEEF). In ArF system, it is premature to use commercialized simulation softwares and ArF resists. To evaluate the real resist system, we made a simple model that uses aerial images. Through the simulation, we calculated MEEFs for 180nm and 130nm line/space pairs in KrF resist system and compared them with experimental MEEFs to obtain the resist blur that satisfies the current experimental MEEFs. With a current KrF resist system, the resist blur is ~0.05 micrometers . In case of ArF resist system, the resist blur is a more important factor in MEEF and must be suppressed to lower than 0.05 micrometers to meet the proper process margin.

To improve power efficiency in a transmitter, a novel method is proposed, this being an uneven multi-level linear amplifier with a nonlinear component (UMLINC). Compared to a normal multi-level LINC (MLINC), the UMLINC employs a new uneven multi-level signal component separator (UMSCS) that significantly improves transmitter efficiency.

The application of the articulation index (Al) model to the fitting of linear amplification was evaluated for 12 subjects with sensorineural hearing loss. Comparisons were made of amplification characteristics specified by the NAL (Byrne & Dillon, 1986) and POGO (McCandless & Lyregaard, 1983) prescriptions, as well as a procedure that attempted to maximize the Al (AlMax). For all subjects, the relationship between percent-correct scores on a nonsense syllable test and Als was monotonic for the two prescriptions, indicating that the Al was effective for comparing conditions typical of those recommended clinically. However, subjects having sloping high-frequency hearing losses demonstrated nonmonotonicity due to poor performance in the AlMax condition. For these subjects, the AlMax condition required much more gain at high than at low frequencies, circumstances that Skinner (1980) warned will cause less-than-optimal performance for individuals having sloping high-frequency hearing loss.

A new type of architecture for an optical Metropolitan Area Network is described, based on establishing controllable, optically transparent paths among network users. The networks in question perform only linear operations on optical signals (power combining, splitting and linear amplification), essentially operating as a dynamically controlled “ether” within which light beams are selectively directed between prescribed source-destination pairs on demand. Because they are controllable, they are capable of being reconfigured in response to changing load conditions or component failures.

A power combiner for nonlinear amplifiers based on the Wilkinson circuit method using lumped elements is presented. Compared to existing designs, the third harmonics of the two different signals, fed into the two input ports of the circuit, are matched and decoupled as well. The circuit is described and theoretical and measured results are presented.

A theoretical investigation is made of the influence of linear amplification as a result of stimulated Brillouin scattering in a multimode fiber waveguide. Calculations are made of the threshold of such scattering and of the efficiency of conversion of a pump wave into a Stokes wave under steady-state and transient conditions. The theoretical results are shown to agree well with experimental results obtained under small-gain conditions.

Application of cathode phase inversion previously described is made to several practical circuits including symmetrical cathode‐ray oscillograph amplification, high fidelity d.c. amplification, and differential or mixer amplifier operation. The theory of a symmetrical degenerative attenuator modification of the basic circuit is developed and practical applications are described.

The line-narrowing and line-rebroadening of the Amplified Spontaneous Emission (ASE) in the high-gain He-Ne 3.39 pm laser amplifier and statistics of intensity fluctuations of the ASE were studied with emphasis on the transition region from the linear amplification to saturation.

Efforts to record evidence of electrical activity from the body surface originating in the His bundle or bundle branches have been reported since 1973. Almost exclusively, these techniques have required digital averaging of 50-100 sequential cardiac cycles. For immediate diagnostic, therapeutic and prognostic application, recording on an every-beat basis is highly desirable. This is especially important in instances of changing atrioventricular conduction, arrhythmias or less-than-constant RR intervals. Our object has been to develop a system for more nearly optimal noise reduction, to avoid the disadvantages of serial signal averaging, and to be able to record His-Purkinje activity in man on an every-beat basis. Using multiple parallel inputs wih linear amplification, additional logarithmic amplification, some bandpass filtering, and a logic circuit that ultimately examines and accepts or rejects a deflection as "true" signal, we can record, in most instances, on a beat-by-beat basis, this very valuable component of the cardiac electrical cycle.

Two MOS current gain cells are proposed that provide linear amplification of currents supplied by several linear MOS V-I converters. The gain is electronically variable by a voltage or a current and can be made insensitive to temperature and IC processing. The gain cells have a constant (gain-independent) bandwidth. >