Showing papers on "Biasing published in 1971"

Studies of tunnel MOS diodes II. Thermal equilibrium considerations

Abstract: The oxide thickness δ of a tunnel MOS diode is varied over the range 10 to 45 A. This is done in an effort to establish the restrictions upon δ for which thermal equilibrium in the semiconductor is a valid approximation under the application of bias. Particular attention is paid to the reverse-bias case, and most of the experimental results are for δ>25 A. A transition is observed from the behaviour of the ideal Schottky barrier to that of the thick-film MOS device. The ac conductance and capacitance together with dc current characteristics are studied as continuous functions of bias. From these results, information is obtained which relates the quasi-Fermi levels for (i) majority carriers, (ii) minority carriers and (iii) electrons in the interface states to δ. Thermal equilibrium statistics are found to be applicable to the semiconductor in the presence of a bias voltage when δgreater, similar30 A, which compares with a theoretical prediction of δgreater, similar13 A.

Sodium Ion Drift through Phosphosilicate Glass ‐ SiO2 Films

Abstract: The field‐assisted transport of sodium ions through phosphosilicate composite films on silicon substrates has been investigated. The effects of concentration (in the 0 to 8 mole per cent [m/o] range), sodium contamination level (between 1011 and 1015 Na+ ions/cm2), field, temperature, and time have been quantitatively determined. For a limited quantity of transported sodium, this quantity is approximately proportional to the square root of biasing time; exponentially dependent on temperature and field, increases linearly with the initial sodium contamination level; and decreases drastically with increasing concentration. For example, seven more orders of magnitude of time are required to drift a given number of Na+ ions through a composite layer than through a 2150Aa thick layer of pure, thermally grown . The results are consistent with a model based on the emission of Na+ ions from traps in the phosphosilicate layer. It was concluded that phosphosilicate glass films, having negligible intrinsic polarizability, can be used to effectively stabilize IGFET threshold voltages against changes (0.1V in 10 yr at 80°C under a field of ) due to the presence of large amounts of sodium.

Microwave properties and applications of negative conductance transferred electron devices

Abstract: The transferred electron effect in epitaxial GaAs has been used to realize a semiconductor device which exhibits a stable negative conductance over a wide range of microwave frequencies and power levels. These devices have been used in conjunction with circulator coupled networks to design high-level wide-band transferred electron amplifiers which have a voltage gain bandwidth product in excess of 10 GHz for frequencies from 4.0 to about 16.0 GHz. Linear gains of 6-12 dB per stage and saturated output power levels in excess of ½ W have been realized. The physical and electrical properties of these devices are described with regard to the achievement of a stable negative conductance. The influence of several parameters (i.e., device temperature, bias voltage, circuit loading, etc.) is discussed with regard to device and circuit stability. Measurements of the terminal admittance of several typical devices as a function of the bias, input power, and frequency have been used to study their microwave properties. The large signal data are used to compute the relationship between the available device power and the magnitude of the negative conductance independent of the test circuit. This same measurement technique can provide a simulation of the performance of any nonlinear negative conductance, without the need for circuit design and load tuning. In addition, an analytical large signal model of the negative conductance has been used to predict the large signal performance of the active device (i.e., gain compression, conversion efficiency, etc.) in both oscillator and amplifier circuits.

Enhanced‐Mode Radiation Detection by Superconducting Films

Abstract: In the course of investigating radiant‐energy detection by high‐resistance superconducting films [≈10 KΩ/square (□)] an unexpected enhanced mode of detection was observed at microwave frequencies. This mode was observed in addition to and differed significantly from the expected thermal or bolometer mode of detection. Since that time detailed measurements have been made of the dependence of the enhanced‐mode response on bias current, incident power, temperature, and sample resistance; these are reported here. Correlation of the characteristics of the enhanced mode with the nonlinear VI (voltage‐current) characteristics of the film is shown. This suggests that the enhanced mode is the result of a nonlinear response to currents induced in the film by the incident radiation, which explains the short wavelength cutoff associated with the enhanced mode. Physical mechanisms which might cause this response are considered and fabrication techniques for these films are presented in detail. Since the initial report...

Automatic bias control for electrostatic development

Abstract: An automatic bias control for development of a latent electrostatic image comprises an electrometer for continuously measuring the level or amplitude of the electrostatic charge in the areas comprising said image and for providing a proportional signal that is used to control the electrical bias applied to development means. The proportional signal is used to drive a circuit containing three serially connected operational amplifiers which are interconnected in accordance with and in timed relation to the location of the image relative to a probe head connected to the electrometer and to a development station. The control signal generated by the circuit is used to drive a voltage supply means whereby a bias field corresponding generally to the amplitude of the charge level of the image background areas is provided so that a minimum of toner particles will be applied to these areas.

LSA relaxation oscillator principles

Abstract: Oversized n-GaAs diodes operating in the LSA mode with doping-to-frequency ratios in the 1-5×105s/cm3range are investigated in circuits that contain a short-circuited high impedance transmission line foreshortened to resonate the electronic parallel capacitance of the diode. By comparing computer simulations with experiments, such diodes are shown to operate in a nonsinusoidal LSA relaxation mode which offers good efficiency, effective space-charge control, and a fast buildup of the oscillations; details of the computer program are also given. A simple analysis is developed which defines the inductive and capacitive time constants controlling the voltage waveshape and explains the frequency tuning with bias voltage and the effective space-charge control. The analysis is shown to be suitable for oscillator design purposes.

Stabilisation mechanism for 'supercritical' transferred-electron amplifiers

Abstract: It is shown that a supercritical GaAs c.w. Gunn diode with a cathode doping notch and doping profile sloping upwards from the cathode to anode may act as a stabilised amplifier at high bias voltage. This profile is similar to that in many present-day devices, and may provide a more practical way of increasing the field uniformity so that the noise figure may be reduced, as described by Thim. It is suggested that this mode of operation may be more relevant to the operation of supercritical amplifiers than other stabilisation mechanisms involving large anode fields.

Semiconductor electronic circuit with semiconductor bias circuit

Abstract: A semiconductor electronic circuit employs a semiconductor bias circuit, in which at least two inverter circuits are provided, each comprising a depletion type MOS transistor and an enhancement type MOS transistor, which are formed on a p-conductivity type semiconductor chip. The depletion type MOS transistor has its gate and source electrodes short-circuited and serves as a load transistor, while the enhancement type MOS type transistor has its drain electrode connected in series to the source electrode of the depletion type transistor. The input terminal and the output terminal of the first inverter circuit are connected to each other, and the voltage obtained at the output terminal is applied as a bias voltage to the input terminal of the second inverter circuit.

Two terminal current limiter

Abstract: A two terminal current limiter is disclosed. The current limiter includes two (first and second) transistors and two resistors, one of which, acting as a sensing resistor, is connected in series with the collector-emitter path of the first transistor between the said two terminals. When sufficient voltage drop occurs across the sensing resistor, the second transistor is biased into conduction, which together with the second resistor, controls the biasing of the first transistor, thereby controlling the current flow therethrough.

Precise method for controlling thickness of a coating

Abstract: AS A COATING COMPOSITION IS DEPOSITED ON A TRAVEL WEB AS THE WEB PASSES OVER A BACK UP ROLLER DISTURBANCES SUCH AS VARIATION IN THE RATE OF WEB FEED, THE THICKNESS OF THE WEB AND/OR VIBRATIONS ARE TRANSLATED INTO AN ELECTRICAL SIGNAL WHICH IS THEN PASSED THROUGH A POLARITY CONVERTER, A PHASE SHIFTER AND AN AMPLIGER. THE RESULTING SIGNAL IS APPLIED WITH A SUITABLE BIAS VOLTAGE BETWEEN THE COATING COMPOSITION AND A SUITABLE ELECTRODE ON THE OPPOSITE SIDE OF THE WEB AT THE POINT OF APPLICATION.

Operating Criteria for Active Microwave Inductors (Correspondence)

Abstract: A method is given whereby the range of frequencies of operation of an inverted common collector transistor circuit (synthesized inductance) is found experimentally as a function of bias current. A complementary relationship is shown to exist between this method and that which gives the frequency range by determining the maximum reflected negative resistance characteristics.

Magnetic modulating system

Abstract: CONSISTING OF TWO RESONANT CIRCUITS COMPOSED OF THE NONLINEAR INDUCTOR AND A CONDENSER. THE OUTPUT SIGNAL OF THE DIFFERENTIAL OUTPUT CIRCUIT CAN BE CONTROLLED ACCORDING TO THE INPUT SIGNAL SO ASD TO MODULATE THE OUTPUT SIGNAL WITH HIGH SENSITIVITY BY MEANS OF A VERY SMALL INPUT SIGNAL. A MAGNETIC MODULATING SYSTEM HAS A MAGNETIC CORE AND TWO RESONANT CIRCUITS WHICH ARE SUPPLIED WITH AN ALTERNATING EXCITING CURRENT AND AN INPUT SIGNAL. AN ALTERNATING DRIVING MAGNETIC FIELD IS APPLIED TO THE MAGNETIC CORE AND AN ALTERNATING BIAS CURRENT IS APPLIED TO A NONLINEAR INDUCTANCE ELEMENT OF A DIFFERENTIAL OUTPUT CIRCUIT

Electrochemical Synthesis and Photovoltaic Effect of Copper Sulfides on CdS Single Crystals

Abstract: Copper-sulfide layer is electrochemically produced on CdS single crystals in copper ion solution with various bias current densities. The compositions and structures of the copper sulfides are determined by means of the X-ray powder and single crystal methods. The phases of the copper sulfides formed on CdS crystals change not only by the bias electric current density but also by the temperature of solution. On examining the photovoltaic effects for all combinations of the copper sulfides and CdS, it is shown that the best combination for the solar cell is the Cu2S-CdS pair.

Controlling multiple voltage levels for electrostatic printing

Abstract: An electrical arrangement associated with the control and operating circuitry for an electrostatic printing machine of the type employing magnetic brush development for controlling the electrical bias on the developing magnetic brushes for enhancing print quality in situations wherein the background or density of an original to be copied is unsuitable for normal mode printing. Along with normal mode printing, there is provided means for biasing the magnetic brushes for originals having dark background or are of low density.

single wall domain arrangement

Abstract: Single wall domain material for which permissible bias field ranges exist for only narrow ranges of temperatures have been found to be particularly useful over relatively large ranges of temperature when used with a biasing magnet which provides a biasing field which varies properly as a function of temperature.

Electrical and optical properties of ZnTe-GaSb heterojunctions

Abstract: Heterojunctions between ZnTe and GaSb is produced by the interface-alloy technique with the use of movable quartz tube loaded in a furnace instead of a strip-heater. X-ray measurement shows that the recrystallized GaSb is monocrystalline and oriented parallel to the ZnTe substrate with (111) as the growth direction. Photoresponse for p-p ZnTe-GaSb heterojunctions decreases exponentially with decreasing incident photon energy for hν < 2·18 eV at room temperature. This behavior is explained by a model of linearly-graded bandgap region of the order of 500 A long, which was first proposed for GaAs-InSb heterojunction by Hinkley and Rediker. The photocurrent is produced by hot holes generated by absorbed photons in the graded-gap region which traverse this region with a mean free path of about 40 A. Space-charge-limited current observed in I–V characteristics of p-p ZnTe-GaSb heterojunctions is explained by Lampert theory. The thickness of semi-insulating region is estimated at about 1 to 3 μm from the capacitance measurements without d.c. bias. This thickness is much larger than the graded bandgap region. Capacitance depends strongly on both forward d.c. bias voltage and a.c. frequency, but is almost independent of reverse bias voltage. The results of capacitance measurements for forward bias are qualitatively interpreted in terms of a change in the trapped charge density in the semi-insulating region. A significant discrepancy between the theory and experimental results exists in the region of trap-free limit.

Self-biasing single wall domain arrangement

Abstract: A zero bias, single wall domain propagation arrangement is achieved by forming a layer of magnetic material in which single wall domains can be moved in stripes having dimensions to be self-biasing. A number of different types of domains are found to coexist in such strips leading to a relatively flexible storage arrangement.

Biasing network for transistors

Abstract: A biasing network for an RF transistor amplifier is provided wherein the bias varies smoothly and continuously from a value below turn on giving class B operation at low power inputs, to a lower valve giving class C operation at higher power levels, and finally, to a point where the DC dynamic impedance between the base and the emitter of the amplifier is extremely low, promoting maximum transistor gain and efficiency. Linear amplification at RF frequencies over the full range of power inputs is achieved.

Beam current limiting circuit

Abstract: A circuit for limiting the current supplied to the cathode of a grid controlled electron beam gun welder. When the current attempts to rise above a predetermined level because of a change of bias voltage, the voltage drop across a sensing resistor approaches that of a zener diode which clamps the base voltage of a transistor in the cathode circuit causing the transistor to shut off sufficiently to limit the current to the maximum set point level. An inductor in the cathode circuit also tends to limit beam current for a short duration change of bias voltage. Several circuits are connected in series.

Current density distribution across the pn junction of a partially contacted diode at high forward bias

Abstract: For some diodes such as pn junction lamps, one region is normally only partially contacted and bounded by a very shallow junction. This can cause considerable voltage losses across the face of the forward biased junction and hence a fall in current density flow into the junction. This current density is calculated for diodes of circular geometry for (i) central circular, and (ii) outer annular contact to the thin region as a function of radial distance, the other region being fully contacted at the back. The current density is assumed to be given by J r = J 0 exp (qV/βkT) where V is the variable local forward bias voltage which results in the thin region being a resistive transmission line with an exponential leakage to ground. Analytic solutions are obtained for J r and these are plotted for realistic geometries and diode parameters. Comparisons of measured values of radial light intensity Br across a diode with an outer annular contact with calculated values shows reasonable agreement if a linear relationship between Br and J r is assumed. In addition to the current I0 flowing into the active area of the diode, the current injected beneath the contact to the thin region, whose resulting light emission is obscured, is also calculated. The voltage losses in the thick, fully contacted region are estimated and shown to be very small.

Input bias and signal conditioning circuit for differential amplifiers

Abstract: The input terminals of the first stage of a multistage amplifier are connected to a network comprising four strings of unidirectional devices. The first and second strings are connected in series and poled in a first direction between the input terminals of the first stage. The second and third strings are connected in series between the input terminals and poled opposite to the first direction. The junctions between the first and second strings and the third and fourth strings are joined and a voltage potential applied thereto. In response to the voltage potential a bias current is conducted to the first stage through the second and fourth strings, the first and third strings being reverse biased. The first and third strings become forward biased to clamp the input terminals to the voltage potential when the magnitude of signal voltage at the input terminals with respect to circuit ground exceeds the magnitude of the voltage potential. The first stage is coupled to a second stage, circuit ground of the first stage being isolated from circuit ground of the second stage and is coupled to a pair of zener diodes which are in turn connected in series and similarly poled and across which is generated an alternating voltage limited in amplitude by the zener voltage of the diodes. The junction of the diodes is connected to the circuit ground of the first stage. A pair of impedances couple current from the diode pair to the input terminals of the first stage. The alternating current applied to the input terminals produces a voltage proportional to any impedance which may be connected between the input terminals whereby such impedance is measured.

LSA relaxation oscillations in a waveguide iris circuit

Abstract: Large-signal computer simulations of GaAs LSA relaxation oscillations in an X-band waveguide iris circuit are presented. The study is focused on a particular oscillator and a realistic model of an experimental circuit is used. However, the results are typical for other LSA relaxation oscillators. Basic features of the microwave circuit, characteristic voltage and current waveshapes, frequency tuning with bias voltage, and oscillator starting transients are discussed. The RF output power is shown to build up in less than ten cycles. Circuit optimization for high dc to RF conversion efficiency is discussed and circuit data for nearly 30 percent efficiency are given. Finally, efficiency degradation is discussed when doping gradients are present, and effciencies of 15 and 10 percent appear possible for doping gradients as high as 20 and 60 percent, respectively. Hence, the LSA relaxation mode is shown to be less sensitive to doping gradients than the sinusoidal LSA mode.

Slow voltage-induced barrier height changes in metal-germanium surface barriers

Abstract: The aluminium-germanium contact has been studied in detail, with particular emphasis on (a) the change of barrier height with time after fabrication and (b) the current changes which take place following the application of a constant bias voltage. Three kinds of germanium surface have been used: etched, cleaved in air and cleaved in ultra-high vacuum. The results can be explained in detail by a model involving slow surface states in the oxide by making two assumptions: (i) that changes take place in the oxide film on the germanium surface after metal evaporation; (ii) that the application of a voltage of either polarity causes charge exchange between the slow states and the semiconductor, which leads in turn to a change in the height of the potential barrier for electrons passing from the metal into the semiconductor.

Theory of segmented metal discharge tubes for argon lasers

Abstract: The length of a floating segment along which a discharge can be maintained is mainly determined by the ratio of electron temperature to electric field. Metal segments several metres long appear possible for favourable values of this ratio. The effect of an axial magnetic field is to reduce the length of floating segment possible. The effects of biasing the segments positively or negatively is discussed. Some problems of discharge initiation are examined.

BIAS‐DEPENDENT STRUCTURE IN EXCESS NOISE IN GaAs SCHOTTKY TUNNEL JUNCTIONS

Abstract: Large‐amplitude excess noise has been observed in the tunneling current of degenerate p‐type GaAs–Au Schottky junctions. At 4.2 K the noise voltage exhibits well‐defined peaks as a function of bias voltage. The background noise exhibits a 1/f‐type spectral response, but the spectral response of some of the peaks indicates that tunneling via surface states with a single average lifetime occurs. Peaks in the noise voltage correspond in bias voltage position with structure in d2I/dV2.

Power supply system for television receiver

Abstract: The vertical deflection windings of a television receiver are coupled directly to the output of a push-pull amplifier comprising a complementary pair of electronic devices. Bipolar voltages for driving the complementary pair are derived from horizontal scansion signals by a pair of oppositely-poled secondary windings on the horizontal output transformer. In a preferred embodiment, a third secondary winding on the output transformer is used to derive a biasing voltage from horizontal scansion signals. The voltage thus derived is utilized to bias a sawtooth generator which supplies input signals to the push-pull amplifier. The signals produced by the sawtooth generator vary in amplitude as a function of the magnitude of the horizontal deflection current.

Capacitively coupled load control

Abstract: Disclosed is a high speed electronic drive circuit integrated on a monolithic chip, utilizing capacitive coupling for selective nodal biasing. The circuit selectively superpositions a higher voltage upon preselected nodes to increase the drive capacity of the device by driving it into a more conductive state. The circuit also provides for faster propagation times by providing for higher input voltages at preselected nodes through capacitive coupling.

Time-domain model of the device/circuit characteristics of a TRAPPAT-plasma mode avalanche-diode oscillator

Abstract: A simple computer model of a TRAPATT diode is described. This model is then interfaced with a time-domain representation of a stepped-impedance coaxial circuit, and a bias voltage is applied. Oscillations are then allowed to build up as dictated by the diode-circuit combination, and the performance of a given diode in a particular circuit may be evaluated.