Tube Amplifier Research Articles

Neutralization and unilateralization

ALTHOUGH various methods of neutralization have been employed for several years in vacuum-tube circuits,1 the unilateralization technique was introduced only recently. This technique is based on a study of the linear, active, four-terminal network theory, which has become increasingly important in the design of transistor circuitry. Although neutralized circuits are usually treated as conventional balanced-bridge circuits, they can be analyzed more systematically as network problems. This paper analyzes both neutralization and unilateralization circuitry by means of the four-terminal network theory, and clarifies the similarities and the differences between the two types of circuits. Typical examples of neutralized and unilateralized vacuum-tube and transistor amplifiers are also given.

An analogue computer technique using magnetic amplifiers

THE foremost requirement to be met in the design of computers for operational use by the military services is that of providing adequate reliability of operation. Such equipment should have a mean life between failures of more than 6 months when operated under unfavorable environmental conditions. This degree of reliability is needed to insure that the equipment will inspire the user's confidence in its functional availability, and that the maintenance load under front-line conditions is kept within the capability of the services. If the designer adopts this precept, then he must limit the complexity of the equations solved in accordance with the inherent reliability of the computer components. Conventional computer elements such as servos, with their vacuum-tube amplifiers, moving parts, and potentiometers, have sufficiently low component reliability that only simple computers will meet the over-all reliability requirements. On the other hand, computers with this degree of simplicity will inadequately meet many job requirements. The best way out of this dilemma is to find new computing techniques which have a higher inherent reliability factor per unit computing operation performed.

Investigations of Noise in Audio Frequency Amplifiers Using Junction Transistors

An investigation of noise from modem junction transistors in audio frequency amplifiers is presented. Different circuit configurations are examined and the effects on noise factor of the input termination and operating point are discussed. At least three distinct sources of noise corresponding to different physical phenomena contributing to total noise are identified. In modem junction transistors shot noise and thermal noise set the ultimate limit of noise in transistor amplifiers, and are frequency-independent over the audio spectrum. Semiconductor noise which follows approximately the 1/f law has been found to be just one contributor to total transistor noise. The concept of equivalent input noise resistance is applied to transistor circuits and a comparison is drawn between noise of transistor and vacuum-tube amplifiers.

Silicon alloy junction diode as a reference standard

THE ADVENT of transistors and junction diodes and their incorporation into telephone equipment has increased the importance of the regulated metallic rectifier as a source of low-voltage d-c power. It has been found possible to replace vacuum tube and magnetic amplifier regulating circuits in these power supplies with equivalent, and usually more compact and efficient, semiconductor apparatus.1

Neutralization and Unilateralization

ALTHOUGH various methods of neutralization have been employed for several years in vacuum-tube circuits,1 the unilateralization technique was introduced only recently. This technique is based on a study of the linear, active, four-terminal network theory, which has become increasingly important in the design of transistor circuitry. Although neutralized circuits are usually treated as conventional balanced-bridge circuits, they can be analyzed more systematically as network problems. This paper analyzes both neutralization and unilateralization circuitry by means of the four-terminal network theory, and clarifies the similarities and the differences between the two types of circuits. Typical examples of neutralized and unilateralized vacuum-tube and transistor amplifiers are also given.

Control frequency unit for telescope drive.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Control frequency unit for telescope drive. Dewitt, J. H. ; Seyfert, C. K. Abstract The system to be described utilizes a precision tuning fork which is electrically driven for the generation of the required ac voltage. This voltage is amplified by a regulated vacuum-tube power amplifier which in turn drives the synchronous drive motor in right ascension. The accurately controlled frequency derived from the fork oscillator may be increased or decreased through the interposition of a motor-driven rotary-phase shifter. Through this means the basic accuracy of the fork oscillator is retained, yet it is possible to vary the over-all drive rate in right ascension continuously and with precision up to a maximum of about 3.5 per cent. Nashville, Tenn., and Vanderbilt University, Nashville, Tenn. Publication: The Astronomical Journal Pub Date: 1955 DOI: 10.1086/107129 Bibcode: 1955AJ.....60Q.158D full text sources ADS |

The scintillation limit in fluoroscopy.

The ultimate performance which can theoretically be obtained with a fluoroscopic imaging device is determined by the quantum nature of the x-rays themselves. In medical fluoroscopy, the available x-ray intensity is set by the permissible patient dose, so that the information carried by the x-rays is quite definitely limited. This fact was first pointed out by R. C. Mason (1) in 1944. Since then, experimental work and calculations have been carried out by several others. The limitation has usually been expressed in terms of the minimum brightness gain of an ideal intensifier in which the perception is limited by the scintillation effect rather than by the observer's eye. Mason estimated that the scintillations would be noticeable at a brightness gain of about 10, and expressed serious doubt as to whether very large brightness gains (i.e. 10,000) would be of interest. An experimental test of the effect was carried out for a particular case by Coltman and Ebbighausen (2, 3). Under conditions equivalent to a gain of 5,000, they found that the contrast discrimination for small objects was not seriously impaired by the quantum noise. Morton (4), in discussing the photon limitations of the eye, ventured the opinion that in x-ray image amplification there was little point in going beyond a gain of 10, since no further information could be obtained from the x-rays. Sturm and Morgan (5), in a more elaborate analysis, arrived at a figure of 50 to 100. With the advent of the first operable image amplifier tubes (6), it became possible to prove directly that at brightness gain of 50 times, no measurable loss in visual acuity could be ascribed to the scintillation effect. At this brightness gain, the visual acuity was still limited by the eye rather than by the instrument. Thus it became certain that some of the early estimates of the scintillation limit were unduly pessimistic. Though Sturm and Morgan's work can be revised to yield a very much higher gain figure when certain previously neglected considerations are taken into account, the subject still remained in a very unsatisfactory state, first because of the wide variance of conclusions, and second because all of the methods were more or less indirect and employed extrapolations and assumptions which had not been adequately tested. The research reported here was undertaken to make a direct determination of the capabilities of an ideal fluoroscope limited only by quantum fluctuations. The problem resolves itself into two parts: first, a determination of the number of significant x-quanta available at the screen; second, a determination of the ability of the eye to integrate a scintillating picture into a meaningful pattern. With these data the performance of an ideal image intensifier over the entire range of fluoroscopic conditions can be predicted. Determination of Available Quanta

Traveling-Wave Amplifers and Backward-Wave Oscillators

This paper presents the theory of the traveling-wave tube (TWT) and magnetron amplifier, and of the corresponding backward-wave oscillators, in a uinified form. Expressions are derived for amplifier gain, and oscillator starting current and tuning properties.

DIRECT CURRENT POTENTIAL AND pH OF SEVERAL VARIETIES OF SKIN NEOPLASMS

A study of 36 subjects having skin neoplasms of three degrees of malignancy is described. The hydrogen ion concentration was determined using a Beckman model G pH meter with glass and calomel electrodes while d-c. potentials were measured using a d-c. vacuum tube amplifier and silver – silver chloride electrodes.The results indicate that there is no correlation between malignancy and absolute value of potential, but a correlation between malignancy and pH difference (pH neoplasm − pH normal) and between malignancy and the 'extra positivity' (absolute d-c. potential − 0.059 pH difference) does exist.

Electric Field Meters

The fundamental principles of electric field measurement by the use of inductors and vacuum tube amplifiers are reviewed. An electric field meter is described that employs a rotating inductor and a synchronous ac generator to provide a sign responsive meter reading proportional to the electric field. The synchronized circuits eliminate moving contact rectifiers and promote calibration stability. A simplified field meter using rectified inductor currents to operate a high-impedance push-pull bridge circuit is also described. Design features are incorporated in both instruments that permit them to operate continuously under unusually severe storm conditions.

Investigation of U-H-F television amplifier tubes

Investigation of U-H-F television amplifier tubes

DIRECT CURRENT POTENTIAL AND pH OF SEVERAL VARIETIES OF SKIN NEOPLASMS

A study of 36 subjects having skin neoplasms of three degrees of malignancy is described. The hydrogen ion concentration was determined using a Beckman model G pH meter with glass and calomel electrodes while d-c. potentials were measured using a d-c. vacuum tube amplifier and silver – silver chloride electrodes.The results indicate that there is no correlation between malignancy and absolute value of potential, but a correlation between malignancy and pH difference (pH neoplasm − pH normal) and between malignancy and the 'extra positivity' (absolute d-c. potential − 0.059 pH difference) does exist.

Investigation of UHF Television Amplifier Tubes

Some essential properties of amplifiers for operation in the UHF television band are discussed with particular reference to stability, gain, and noise factor. Various types of tubes have been evaluated, including the Western Electric 416A and 417A; RCA pencil triode; General Electric 6AJ4 and 6AM4; Sylvania 6AN4, and other tubes of special construction.

Modification of Beckman Spectrophotometer with External C Battery Supply and Voltage-Checking Arrangement

Abstract : Several objections are noted to inverting the Beckman Spectrophotometer whenever C batteries and/or plate or screen voltages of the amplifier tubes need changing. These objections become more serious in cases where the optical alignment of accessories cannot be disturbed by movement of the instrument. A modification is described for placing the C battery supply external to the spectrophotometer and incorporating a voltage-checking arrangement. Circuit diagrams for pre-and post-conversion are presented for the components, all of which are normally available from an electronics stockroom.

An accurate electronic whitenessmeter

A rigid and fast acting photoelectric whitenessmeter is described. By varying the cathode resistance of an amplifier tube the use of precise optical measuring devices is avoided. An averaging mechanism is included. The accuracy for non-rotating samples is of the order of 0.1 per cent.

An Infrared Spectrograph for Use in the 40–150-Micron Spectral Region*

Problems relating to the design of a far infrared spectrograph are discussed. The design of a spectrograph which was constructed is described. A platinum strip coated with thorium-oxide is used as a source. Discrimination against short-wave radiation is provided by quartz, paraffin, turpentine soot, a compensated potassium bromide chopper, reststrahlen plates, and a grating (used as a reflection filter) with groove separation somewhat less than the wavelength being investigated. As a dispersing device, an echelette grating ruled with 180 lines per inch is used. The detector is a Golay pneumatic cell. A low noise vacuum-tube amplifier renders the signal from the detector suitable for operation of a strip-chart recorder. The spectrograph is evacuable.Spectral operating characteristics of the instrument are shown in ammonia and atmospheric water vapor spectra in the region between 45 and 150 microns. Absorption lines separated by less than 1 cm−1 are well resolved throughout this spectral region.

A Time Constant Meter for Tuning Forks and Other High Q Devices

The time constant meter described operates on the principle that differentiation of an exponentially decaying rectified envelope decreases it in inverse proportion to the time constant and reverses its sign. Hence, it is possible to obtain a null by balancing the differentiated signal against a portion of the original. The circuit is simple, requiring only one amplifier tube and a tuning eye.

Quartz-Crystal Measurement at 10 to 180 Megacycles

A method is described for measuring the equivalent parameters of both the main and spurious modes of very high-frequency crystal units. The crystal is placed between the plate and cathode of an amplifier tube, and the voltage developed across it is recorded as a function of frequency. The series resistance R88. can be obtained by comparing the resulting voltage peaks with the voltage developed across a pure capacitive load. The series capacitance C8 is measured by recording the resonance curve with the crystal unit in circuit, and then recording a second resonance curve when the capacitance across the crystal unit has been increased by a known amount. The frequency difference between the two curves gives a measure for C8. Correction functions are derived for evaluating the recorded data for crystal units having high R8 and low reactance of the static capacitance Co.

A simplified 60 cycle carrier system capable of measuring low pressures.

Amplification systems for the recording of pulsatile pressure changes using a transducer device have had disadvantages in our hands in ease of operation, stability of the recording mechanism and lack of sensitivity. Previous investigators (1-3) have demonstrated the fidelity and accuracy of resistance wire manometers in the registration of pressure changes derived from intracardiac catheterization technic. Recently, West and associates(4) have described an “inexpensive” carrier amplifier for use with a resistance wire-type manometer and indicated the advantages of such an A.C. amplification system. The following section describes a greatly simplified 60-cycle carrier system of markedly increased sensitivity, which can be phase sensitive and has given satisfactory biological records using a direct recording device without optical magnification. Description of system. The components of our recording equipment are a Statham P23 A+ pressure transducer, a 60-cycle carrier supply system, the balancing network, amplifier, power supply and recorder. Circuit diagrams (Fig. 1 and 2) present the arrangement and design of the apparatus. The power supply is the conventional 400 volt nonregulated and 250 volt regulated type. Line frequency of 60 cycles is fed into the transducer by means of a filament transformer. The transducer output is then fed into a 500 ohm line to grid transformer coupling to a high gain, push-pull amlplifier. A Zero balancing system is also fed into this coupling transformer which acts to balance out the output of the transducer when no pressure is being applied. The signal is picked off the filament transformer used to operate the amplifier filaments. Proper phase is determined by interchanging the primary leads. The zero balancing control is a potentiometer on the output of the balancing amplifier tube. By unbalancing this control or zero set in the proper direction either positive or negative pressures may be recorded; this makes the system phase sensitive.

Temperature Regulation in Induction Heating

This paper describes an improvement in the design of a temperature regulator for induction heating that was the subject of a previous report from this laboratory. The improved design eliminates the optical lever by use of vacuum tube amplifiers. The result is to improve sensitivity and eliminate the large time constant of the galvanometer used in the earlier circuit. In experiments on vapor pressure of iron and cobalt at 1200°—1500°K, the new regulator held temperatures of the iron or cobalt samples constant to within about 0.1 percent of the absolute temperature.