Showing papers on "Biasing published in 1970"

Thermal and optical emission and capture rates and cross sections of electrons and holes at imperfection centers in semiconductors from photo and dark junction current and capacitance experiments

Abstract: Photo and dark current and capacitance transient experiments are described which can provide highly accurate and unique data of the electronic properties of impurity centers in semiconductors such as energy level, multiplicity of charge state, thermal and optical emission rates, thermal capture rates, thermal and optical cross sections and the dependences of the rates and cross sections on sample temperature, static electric field and photon energy. These experiments are grouped into four categories in the discussion according to the temperature (below and above freeze-out or negligible and finite thermal rates) and presence or absence of optical excitation at the impurity center. Each category is subdivided into a number of cases according to the method used to set the initial charge state of the impurity center prior to the measurements. Methods of setting the initial state include electrical switching of the bias voltage and optical excitation using either interband or band to impurity monochromatic light. Experimental examples are given for many of the experiment methods discussed.

Ovonic threshold switching characteristics

Abstract: The Ovonic Threshold Switch ( ots ), a two-terminal symmetrical voltage sensitive switching device, is a new circuit element, and must be characterized before it can be used in a practical manner by circuit designers. The purpose of this paper is to perform that task. The ots is characterized in terms of both its static and dynamic parameters. A study is made of the blocking state and of the conducting state of the ots . Experiments on switching, both from the blocking to the conductive state and vice versa, are discussed. Also included is a study of energy and charge switching requirements and the effect of pre-breakdown bias voltage and polarity reversals on the turn-on mechanism. The static and dynamic parameters are characterized in terms of temperature, device geometry and other parameters. It is shown that polarity reversals during the pre-breakdown period do not affect delay time and that pre-bias reduces delay time independently of polarity.

Direction finder system

Abstract: A high frequency radio direction finder receiver system of the over-lapping lobe switching type utilizes an array of lineal antenna elements formed of crossed multiple-element receiver antenna systems sharing one directly coupled receiver antenna element in common. Lobe switching is afforded through bias voltage control of a characteristic of the elements by semiconductor switching circuits.

A thin-film inductance using thermal filaments

Abstract: A particular thin-film structure is analyzed to determine the conditions for thermal filament formation. Assuming that these conditions are satisfied and that the structure is electrically biased so that a thermal filament exists, the current-voltage characteristic and small-signal equivalent circuit for a general conductivity-temperature characteristic in the thin film are determined. It is shown that an abrupt or discontinuous change in conductivity with temperature of the type observed in materials exhibiting semiconductor-metal transitions is not necessary to obtain thermal filaments. It is also shown that if there is no thermal hysteresis in the conductivity -temperature characteristic of the thin film, the filament equivalent circuit for the particular structure analyzed is closely approximated by a resistance in parallel with an inductance. The thin-film prop. erties required for this inductance to be independent of both the ambient temperature and the bias current are defined. If thermal hysteresis exists, the analysis shows that small-signal distortions occur, the inductance will become frequency dependent at low frequencies, and a nonlinear resistance must be added to the equivalent circuit in series with the inductance. Measurements on this structure using VO 2 as the thin-film material are presented and discussed, and are shown to verify the conclusions based on the analysis.

Efficient low voltage piezoelectric power supply

Abstract: An electric device for efficient transfer of power from a piezoelectric crystal source to a capacitor. The piezoelectric crystal is coupled to a transformer, the secondary of which is shunted by a series combination of a rectifying device and a storage capacitor, all in such manner that energy is transferred from the piezoelectric crystal, essentially a first capacitance device, to the storage capacitor, a second capacitance device, with a new order of efficiency. In a specific embodiment of the invention the piezoelectric crystal and two capacitances are associated with biasing networks and a transistorized switching circuit and a firing circuit in such manner that the energy transferred into the storage capacitor is utilized to fire a squib.

Constant current source

Abstract: An improved constant current source, which may provide very small current without requiring the construction of a large resistor, is disclosed. This constant current source includes a transistor having a bias source comprising a second transistor that is biased to low current conduction, the biasing resistor for the biased transistor being advantageously small.

An analysis of current saturation mechanism of junction field-effect transistors

Abstract: A two-dimensional numerical analysis has been amde for junction field-effect transistors with small and large values of length-to-width ratio. Comparison of the results for different drain bias voltages shows the cause of the saturation of the drain current and the finite differential drain conductance in the saturation region. The effects of the geometry of the device and the field dependent mobility to the drain characteristics are clarified. Detailed pictures of the free carrier density distribution are presented, and the minimum channel width and the channel length are given for various bias conditions. A conduction path from the source to the drain with appreciable free carrier density has been found for bias conditions normally considered as pinched-off conditions. The drain characteristic with gate bias voltage is seen to be equivalent to that of a device with correspondingly smaller width and zero gate bias.

A high-gain 15-W monolithic power amplifier with internal fault protection

Abstract: A combination of circuit and device innovations has resulted in the development of a 15-W integrated-circuit power amplifier that incorporates a preamplifier on the same chip to give an overall closed-loop gain of 60 dB. Two novel devices used are a new high-frequency drift-lateral p-n-p to improve stability and a new 3-A n-p-n power transistor design with individual emitter ballasting to achieve a larger safe-operating area. Other interesting features are an externally adjustable short-circuit current limit, a built-in thermal shutdown circuit that automatically limits the junction temperature to 175/spl deg/C, an electronic shutdown control to mute the amplifier; a supply voltage range of 10-40 V, excellent power-supply rejection (55 dB), and a unique biasing technique that ensures that the output quiescent point remains at one-half the supply voltage with the total bias current changing only 3 mA over the complete supply voltage range (10-40 V).

High peak-power LSA operation from epitaxial GaAs

Abstract: Gallium solution epitaxy, using a steady-state, temperature-gradient technique has been successfully used to grow high-quality, 150-µM thick gallium arsenide layers with less than 5 percent variation in electron density. A laser-probe, photoconductivity method has been used to precisely measure the relative variations of electron density. Using these epitaxial layers with 1.5-2 ×1015cm-3electron concentration, LSA oscillations at X- and Ku-bands have been measured with up to 400-watt peak power and with more than 10 percent efficiency. A small iris circuit with a stepped ridge waveguide impedance transformer has delivered fundamental LSA oscillations in the X- and Ku-bands. Operating bias levels of up to 20 times threshold were observed on some diodes. The importance of the substrate (and contact) layer conductivity at the interface with the active layer, as well as the skin depth of the active layer, for efficiency and in preventing avalanche breakdown is explained. Frequency tuning with bias voltage and temperature is shown and discussed.

Broad-Band Equivalent-Circuit Determination of Gunn Diodes

Abstract: A method has been developed for the direct broad-band measurement of the impedance of a Gunn diode operating at a bias voltage exceeding threshold. This method is based upon determination of an equivalent-circuit model for the diode mount and package, which is found to be valid over the 1- to 20-GHz range. Using this circuit, the low-field diode equivalent circuit is found and takes the form of a parallel RC circuit as expected from the theory. An unusual result is that the low-field capacitance is found to be strongly dependent on the bias voltage; this dependence is presumed due to the free-carrier contribution to the effective dielectric constant. Some direct broad-band measurements are reported for an active Gunn diode biased beyond threshold. These measurements provide additional insight into the conditions under which significant parametric action may occur in a Gunn diode.

Magnetically Tunable Microwave Bandstop Filters Using Epitaxial YIG Film Resonators

Abstract: Disk samples of epitaxially grown YIG, of significantly higher aspect ratio than are available with flux‐grown YIG, can be easily fabricated for electronically tunable filter applications and are amenable to integrated circuit construction techniques and multi‐channel operation. To determine the utility of epitaxial YIG resonators (190‐mil diameter and 20‐μm thick), bandstop filters using necked‐down strip transmission line with YIG close to the stripline were tested. Tuning was achieved by varying the biasing magnetic field applied parallel to the plane of the YIG film. Adequate coupling was achieved by surrounding the transmission line and resonator with dielectric materials and by reducing the impedance level presented to the resonator. The external quality factor Qe was thus varied between 10 and 100. The devices were designed to operate from 2 to 3 GHz and exhibited an off‐band insertion loss less than 1.0 dB. Maximum attenuation at center frequency decreased as the 3‐dB bandwidth decreased in accord...

Kerr cell system for modulating a laser beam

Abstract: The electro-optical telemetr system of the present invention includes a laser, polarizer and analyzer elements and a Kerr cell modulator containing a parallel plate transmission line immersed in a birefringent liquid such as nitrobenzene. The modulating signal is applied to the parallel plate transmission line which is terminated in its characteristic impedance. Preferably, the laser beam is directed into the modulator at an angle equal to WHERE N AND E ARE THE INDEX OF REFRACTION AND THE DIELECTRIC COEFFICIENT, RESPECTIVELY, OF THE BIREFRINGENT LIQUID. Two parallel mirrored surfaces may be used to make the laser beam traverse the modulator a plurality of times. An environmental chamber containing a liquid bath and a thermo-electrical control system may be utilized to maintain the temperature of the modulator at a predetermined point. The Kerr cell modulator may also be biased by a bias voltage provided by a high voltage bias supply controlled by a feedback system utilizing another laser.

Modification of the Charpak Chamber with Foil Supported Conductors

Abstract: A conductive film supports the anode wires of a multi-wire proportional type counter and a bias voltage applied through this film controls the electric field concentration around the anode wires. Because the critical operating voltage is applied through the film one has increased freedom in the mechanical design of these chambers . Two coordinates of spacial information are available with this technique. The first coordinate is the anode wire signals. The second is obtained by a grid of ribbons on the back of the anode supporting film which picks up an induced signal from the primary discharge. Spacial resolution of 1.6 mm fwhm has been measured using the induced readout ribbon grid along with 3.3 mm fwhm on the anode grid. We expect this to improve.

Fault indicator circuit for vehicular battery charging systems

Abstract: First and second Zener diodes respectively connecting first and second output terminals of a differential amplifier to the base of a transistor, the collector of which is connected to an indicator lamp and the emitter of which is grounded. One input to the differential amplifier is connected to a point in the charging system for the vehicle battery such as the output winding of an alternator, and the other input is connected to a reference potential that varies with the rectified output voltage of the alternator. When the output of the charging system varies from predetermined levels, one or both of the Zener diodes break down to bias the transistor into conduction, thereby illuminating the lamp. Otherwise the Zeners effectively remove the bias voltage from the base of the transistor keeping it off.

Computer for use with ring laser rotational rate sensors

Abstract: A computer responsive to the pulse sequence output signal of a ring laser rotational rate sensor having contra-rotating beams and biasing means to prevent mode locking. The biasing means selectively changes the effective optical path length around the ring of one of the beams with respect to the other. The pulse repetition frequency of the laser output pulse sequence is representative of the difference in oscillation frequency between the contra-rotating beams. The computer comprises a bias control circuit for selecting the polarity of the bias applied to the ring and includes a compensation circuit for providing a bias compensation pulse sequence whose pulse repetition frequency is representative of the magnitude of the applied bias. The computer in addition provides signals representative of the polarities of the laser output pulse sequence and the bias compensation pulse sequence respectively. The laser polarity is chosen in accordance with the selected polarity of the applied bias. The polarity of the bias compensation pulse sequence is chosen opposite to the selected laser polarity. A pulse sequence combining circuit is included for combining the laser output pulse sequence and the bias compensation pulse sequence thereby providing a combined pulse sequence. The pulse sequence combining circuit furthermore combines the associated polarity signals thereby providing a combined polarity signal. The combined pulse sequence is integrated in accordance with the combined polarity signal for providing a signal representative of the ring about an axis normal thereto.

Ttl input array with bypass diode

Abstract: A transistor-transistor logic gate characterized by a low inverse alpha current and high noise margins includes a multiemitter input array and a unique biasing arrangement This arrangement comprises a diode-connected transistor in combination with a pair of resistors connected across the base-collector junction of the multiemitter transistor for maintaining an optimum biasing voltage across the base-collector junction of the multiemitter transistor regardless of the value of signals applied at the emitters thereof

An isotype heterojunction detector for use in pyrometry

Abstract: The utilization of the photovoltaic properties of CdSe-Ge n-n heterojunction as a wide range pyrometer is described; the method is a variation of the two colour technique. The optical response of the heterodiode depends on the bias voltage in such a way that the photovoltage produced by white radiation can be biased to zero, thus providing a null detector. For a specific spectral distribution of energy produced by a black body radiator within the bandwidth of the device there exists a unique bias voltage for which the photovoltage is zero, and the bias voltage can be calibrated directly in terms of temperature. The sensitivity of the detection is 0?6 mV K?1 at 1000 K, 0?1 mV K?1 at 2000 K and 0?05 mV K?1 at 3000 K.

Performance of broad-band microwave-biased extrinsic photoconductive detectors at 10.6 µ

Abstract: An analysis of the photoconductive gain-bandwidth product and SNR is presented, which allows a comparison of microwave-biased and dc-biased extrinsic detectors. The results of an experimental comparison using mercury-doped germanium at 10.6 μ are described. For equal bandwidth of 70 MHz, the measured gain and detectivity were better by a factor of 35 for microwave biasing compared to dc biasing.

Synchronous detector control

Abstract: A synchronous detector includes a differential amplifier section formed from two transistors with input signals applied to their base electrodes and output signals taken from their collector electrodes for application to an included synchronous switching section. A current source section is also included to supply substantially constant quiescent current to each of the transistor emitter electrodes, while a control section is additionally included for diverting some of this current away from the differential amplifier transistors when it is desired to reduce the gain of the detector or inhibit its operation. The electrical control section, however, re-inserts the diverted current into the switching section at a point such that the direct output voltage of the detector does not change as the gain is reduced or as its operation is inhibited.

Constant current series regulator with control of bias current energizing control circuit of the regulator

Abstract: The regulation of the current output of a series type current regulator is significantly improved by closely regulating the bias currents required by the control and reference elements of the regulator. These regulated bias currents may be coupled to the output circuit and form part of the output load current. The regulated bias currents are utilized to energize a reference voltage source and a voltage comparison circuit which in turn control the series regulating device of the current regulator.

Response of highly damped josephson junctions to external, low-frequency noise currents.

Abstract: The dc characteristics of superconducting point-contact junctions subjected to external noise currents are measured under the condition that the noise-frequency spectrum is below the Josephson frequency. It is shown that the curves are in agreement with a model based on modulation of the noise-free dc characteristic. Although in the low-bias-voltage region the shape of the curves is qualitatively similar to previous theoretical predictions for the case of high-frequency noise, for higher voltages the shapes are different. Quantitative differences exist over the whole range of bias voltage.

Bipolar input bistable output trigger circuit

Abstract: A bistable trigger circuit responsive to bipolar input signals having a bias network coupled to the inputs of a basic operational amplifier for providing bistable output signals. The biasing network includes a single variable resistor which provides adjustment of the bistable trigger reference voltage. The output of the operational amplifier changes state for positive or negative variations of the bipolar input signal, greater or less than the preset value of the variable reference voltage.

Biasing Circuitry for Tunnel Junctions

Abstract: A method of generating bias has been developed which greatly facilitates studying the voltage‐current characteristics of tunnel junctions. A triangle wave to sweep the bias, a dc level for offset, and a small amplitude sine wave used for taking derivatives are all summed in a dc amplifier. The junction is biased by the attenuated output of this amplifier with either a high or low impedance load line. The two transistor circuits which largely comprise this bias supply are compact and battery powered, minimizing grounding problems.

Voltage regulator with continuously variable dc reference

Abstract: 1,254,718. Automatic voltage control; automatic current regulation. MOTOROLA, Inc. Dec.5, 1968 [Jan.29, 1968], No.57717/68. Headings G3R and G3X. A voltage regulator of the type wherein a series transistor 26 is connected between D.C. input and output terminals 27, 29 to maintain a constant output voltage, comprises a differential amplifier formed by transistors 20, 22 whose bases are respectively connected to a reference voltage and to the output terminal 29, the latter connection thereby providing a feedback to the amplifier of 100% of the output voltage. Transistors 24, 26 form a Darlington current gain output stage between the amplifier and the output terminal 29, the collector of the transistor 20 being connected to an intermediate point in this stage to ensure transistor current gain at low values of load current. A discussion is given of the advantages of the described arrangement over a known differential amplifier, Darlington stage voltage regulator, Fig. 1 (not shown). The reference voltage for transistor 20 is supplied by a circuit 51 having emitter-coupled transistors 32, 34 in a Darlington type connection with transistors 36, 38, to whose bases are respectively applied a reference voltage V REF IN and a fraction of the reference voltage applied to the base of transistor 20. The circuit 51 acts as a further voltage regulator to control a transistor 54 connected to the input terminal 27, so that the voltage applied to the base of transistor 20 is maintained at a reference value V REF OUT . The reference voltage V REF IN is obtained from a bias circuit 49 having a constant current source 65 supplying a Zener diode 43a so that the ripple feedthrough from input 27 is reduced. The voltage drop across the resistor 61 establishes a reference voltage for constant current sources 65, 67, 25 having a common current sink formed by transistor 52. The arrangement of the source 65 is such that variations in the current gain of transistor 42 are automatically compensated, the transistor 42 having a high output impedance which reduces the effect of input voltage ripple on the Zener diode 43a and the differential amplifiers biased by the sources 67, 25. The circuit 49 also includes a temperature compensating network formed by members 46, 48, 50, 73, 75, 77, of which the emitter current of transistor 46 establishes the bias levels for the current sinks 52, 86, 92 and the collector current of transistor 46 sets the current levels in the sources 65, 67, 25. The transistor 46 is chosen so that the emitter and collector currents are equal and thus all the current sinks and sources are referenced by the same current, which has a zero temperature co-efficient due to the network 46----77 previously mentioned. Since the circuit 49 is independent of the input voltage, application thereof will not start the regulator by biasing the Zener diode 43a into conduction. Hence a circuit 47 is provided which responds to the application of the input voltage to activate the source 65 and cause Zener diode 43a to conduct, thereby providing the reference voltage V REF IN . To "shut-down" the regulator, a positive voltage is applied to terminal 96 causing a clamping transistor 100 to conduct and all the current sources and sinks to "zero", the only bias drain remaining being the current through the resistor 83. Overcurrent protection is provided by a current sensing resistor R sc , which "thresholds" diodes 97, 98, 99 to by-pass the transistors 24, 26 and drive the transistor 45 into conduction, these two actions causing the output voltage and the reference voltage V REF OUT at point 35 to fall to zero. Components 47, 49, 51, 53 may be combined into a monolithic form and externally connected to capacitors 87, 89, which perform stabilizing and noise limiting functions.

Electrical compensation circuit utilizing two transistors connected in parallel

Abstract: A pair of transistors are connected in parallel with the emitters of the transistors connected to ground and the collectors connected together and to a common junction which in turn is connected through a resistor to an output terminal. A first input terminal is connected through an amplifier and a resistor to the common junction. The output of the amplifier is also connected through a diode to the base of the first transistor. The base is also connected through a resistor to a negative biasing voltage. The base of the second transistor is connected through a resistor to a negative biasing voltage. The base of the transistor is also connected through a diode to a second input terminal. The transistors are biased such that a signal appearing on the first input terminal is determinative of the amount of signal compensation appearing at the output terminal and a signal appearing at the second input terminal is determinative of the existence of the compensation.

Gridded crossed field traveling wave device

Abstract: A high-power high-frequency device is disclosed having a thermionically actuated cold cathode secondary electron source and means for controlling electron beam current interacting with energy on either a reentrant or nonreentrant propagating structure. In an exemplary embodiment a grid-controlled primary electron source is coupled to an array of individual secondary electron emissive members biased at sequentially varying voltages. The primary and secondary electron emitters are spaced apart a distance of approximately one electron cycloid path. Such emitters are disposed within a section of a cold cathode source of substantial size. Impingement of electrons upon each successive secondary electron emitting surface results in an electron emission multiplication process heretofore unattainable with cold cathode structures actuated simply by pulses of the input RF energy to be amplified. Operation of the device may be rapidly terminated by biasing of the grid-controlled electrode having very low voltage requirements with the current in the electron beam and power output decaying to zero in a relatively few revolutions of the electron spoke around the cathode structure.

Combination motor-clutch apparatus

Abstract: A combination motor-clutch assembly wherein the input and output members of the clutch are normally held in driving engagement by a biasing means, and having an electromagnetic coil which induces a magnetic field in the output member to overcome the operation of the biasing means and to move the output member axially to control the torque transmitted between the input member and the output member and to effect disengagement of these members.

Small signal lumped model for IMPATT diodes

Abstract: A small signal lumped model of a general IMPATT diode is presented. By applying state space analysis techniques the model is used to predict the small signal impedance of both pn and pin IMPATT diodes as a function of frequency and d.c. bias current. A lumped element equivalent circuit for the microwave cavity in a Read diode coaxial oscillator is derived. Using a state space description of the diode-cavity configuration, the variation of small signal oscillation frequency with d.c. bias current is evaluated.

Sawtooth tone generating and keying circuit for an electronic musical instrument

Abstract: A circuit is provided for generating an output signal having the characteristics of a natural musical tone by converting a square wave input signal into a sawtooth wave output signal. The circuit includes a unidirectional current device and a biasing circuit providing a gradually changing bias voltage to the unidirectional current device. The circuit thereby produces a sawtooth wave output signal of gradually increasing and diminishing magnitude. Circuit arrangements are also provided for combining the musical tones produced by a plurality of such circuits.