Showing papers on "Rise time published in 1990"

An improved return stroke model with specified channel-base current

Abstract: An improved return stroke model that is both physically oriented and has a relatively straightforward mathematical basis is proposed. The current at the channel base is specified, and a time-dependent discharging of the charge stored on the leader channel determines the channel current as a function of height and time. The discharging process is separated into (1) the exponential discharge of the leader head and leader core with a relatively short time constant, less than 1 μs, which we call the “breakdown” time constant, and (2) the exponential discharge of the charge stored around the leader core with a longer time constant, of the order of microseconds. If a typical measured channel-base current is assumed and if the discharge time constants are properly chosen, electric and magnetic field wave shapes calculated with the model exhibit all the significant characteristics of measured fields. From a comparison of calculated and measured field wave shapes, we find a ratio of the breakdown time constant to the channel-base current rise time between 1 and 5. Comparison of typical characteristics of field wave shapes from natural and from artificially initiated (triggered) lightning indicates a faster discharging process for triggered lightning. Depending on the breakdown time constant, the return stroke speed determined using the well-known formula for the transmission-line model, with inputs being the peak electric field and peak current from the present model, are in the range from about 50 percent to 90 percent of the return stroke speed assumed in the present model. The corresponding transmission-line model speeds determined from the peak derivatives of the electric field and current are in the range from about 140 percent to 160 percent of the assumed return stroke speed. These results supply some indication of why transmission-line model speeds determined from the ratio of measured peak current and field derivatives in triggered lightning are greater than the speeds determined from the ratio of measured peak currents and fields. For a given channel-base current, the initial peak electric field and field derivative derived from the model increases as the height above ground of the strike point increases. The new model can therefore explain the differences in the data obtained from the triggered lightning studies at Kennedy Space Center in 1985 and in 1987 as being due to the different height of the triggering structures in those two years. If natural lightning strikes an elevated object, the increase of the initial electric field and field derivative can result in an additional substantial error in determining the peak current and peak current derivative from the transmission-line model.

Considerations for high data rate recording with thin-film heads

Abstract: The significance of head inductance and eddy currents in limiting field rise times is discussed. Poor rise times can cause severe distortion and loss of performance at high data rates. A simple reluctance model is developed to explore the relationship between the geometry of a head and its inductance. The model is extended to include the effects of eddy currents, and to allow the frequency-dependent efficiency (hence the field rise time) to be calculated. Based on this rise time, a geometric model is used to calculate the positions of the recorded transitions and the resulting transition-shift distortion. Experimental results at transition separations down to 6 ns reveal a strong write current dependency which is not seen in the model. This dependence is, however, clearly seen in a simple domain wall model which implicitly includes magnetic saturation. Transition shift distortion can be mitigated by the use of precompensation. It is found that it is possible to successfully recover data at 180 Mbit/s using a conventional thin-film head. >

Power-on-reset (POR) circuit having power supply rise time independence

Abstract: An output of a power-on-reset (POR) circuit is coupled to another circuit which needs to have the logic states thereof reset during each time a power supply used to power same is switched on. The POR circuit includes a first input circuit for generating an output signal that tracks the power supply output voltage Vdd approximately a first predetermined threshold below Vdd, as Vdd ramps up and further includes a second input circuit which generates an output signal which tracks approximately a second predetermined threshold above a second fixed voltage level, e.g., ground. The POR circuit further includes a comparator which compares the output signals from the first and second input circuits and switches an output signal thereof from a first to a second logic state once the input circuit output signals cross each other. A buffer is typically coupled to the output of the comparator to limit loading on same so as not to affect the comparator switching point.

A power control method for a voltage controlled power amplifier and circuitry used in the method

Abstract: In a digital radio telephone transmitter an output pulse with eg cos 2 -shaped edges is produced by a voltage controlled power amplifier (4) When known control loop circuitry is used, the power (Pout) of the output pulse will rise almost step-wise at the beginning of the pulse, which leads to the spreading of the spectrum and to rise time delays of the output pulse with respect to the control pulse (TXC) at different power levels According to the invention a good cos 2 -shape of the output pulse (Pout) and its tracking of the control pulse (TXC) almost without delay is achieved so that a squarewave pulse (V p ) is added to the control voltage (V2) of the power amplifier (4), the pulse (V p ) starting and ending substantially at the same time as the control pulse (TXC) In a preferred embodiment the squarewave pulse (V p ) is added to the control voltage (V2) only during that time when the control voltage (V2) is below that value, at which the control loop begins to operate

Dual purpose pyrometer for temperature and solidification velocity measurement

Abstract: A dual purpose pyrometer is described that allows both accurate radiance temperature measurement and fast temporal response. The system uses two silicon photodiodes with separate optical paths derived from a common spot on the sample. The optical bandwidths and response times of each detection circuit are tailored to the function of each radiometer. The radiance temperature of electromagnetically levitated metallic samples is measured over a narrow optical bandwidth with a high-gain silicon detector. The velocity of solidification of undercooled melts can be deduced from the rise time of the second silicon detector which samples a broad optical bandwidth and has a fast response time. Results from experiments on the undercooling and solidification behavior of electromagnetically levitated pure nickel show that the solidification velocity approaches 17 m/s at high undercooling.

275 GHz 3-mask integrated GaAs sampling circuit

Abstract: A monolithic GaAs diode sampling head with 275 GHz ( −3dB) bandwidth gated by a nonlinear-transmission-line (NLTL) strobe pulse generator and fabricated using three masks at 3 μm resolution is reported. The sampling circuit step response, measured using a second NLTL as a testsignal, showed a l.9 ps (10–90%) convolved falltime and 24% peak to peak ringing.

Light emitting diode drive circuit

Abstract: A light-emitting diode drive circuit comprising a current feeding circuit (3) having a first transistor (16) which receives at the base thereof a first drive pulse signal (S3) sent from a signal receiving circuit, and a second transistor (15) of which the collector is connected to a light-emitting diode (2), of which the emitter is connected to a current source (24) together with the emitter of the first transistor (16), and which receives at the base thereof a second drive pulse signal (S2) having a phase opposite to that of the first drive pulse signal (S3); a fall time shortening circuit (6) including a third transistor (13) which is connected in parallel with the light-emitting diode (2) and which, in response to its base input, short-circuits both terminals of the light-emitting diode (2) at the time of turn-off; and a rise time shortening circuit (5) including a circuit (4) that generates a peaking current at the time of turning the light-emitting diode (2) on and a fourth transistor (14) that is connected in series with the third transistor (13) and adds the peaking current to the drive current when the light-emitting diode (2) is turned on. The circuit shortens the rise and fall times of light pulses outputted, improving the response speed of even a light-emitting diode (2) having poor intrinsic response characteristics, for example, a light-emitting diode which emits red light in a short wavelength band.

Cryogenic voltage-sensitive preamplifier using GaAs MESFETs of low 1ƒ noise

Abstract: A voltage-sensitive preamplifier using GaAs MESFETs of low 1 ƒ noise has been developed. The voltage gain is fixed to 51. With a total power dissipation of 54 mW the preamplifier's series noise level at 4 K is 9 nV / Hz 1 2 at 100 Hz and 0.3 nV / Hz 1 2 at 100 kHz. The input bias current of the preamplifier was determined to be lower than 10 fA below 100 K. Response to a step pulse gave a rise time of 40 ns when loaded with a 130 pF load. The voltage-sensitive preamplifier is presently used in Milano for signal readout and characterization of large-mass bolometric particle detectors. An energy resolution of 13 keV for the 1330 keV of a 60Co gamma source was obtained with an 11 g Ge bolometric detector readout with this preamplifier.

Control circuit having outputs with differing rise and fall times

Abstract: A control circuit suitable for generating control signals for controlling the bit and select lines for a static RAM and also for use in a buffer for reducing transient current and for controlling the slew rate. The circuit comprises a pull up and a pull down transistor, each having a first and a second terminal, and a passing gate connecting the second terminals of the two transistors. The gates of the two transistors are controlled by a signal. A first control signal at the second terminal of the pull up transistor has a fast rise time and slow fall time with respect to the input signal and the second control signal at a second terminal of the pull down transistor has a fast fall time and slow rise time with respect to the input signal. When the control circuit is used for controlling a static RAM, the passing gate is always turned on. The two control signals are then used to control the bit and select lines of the static RAM. When a control signal is used in a buffer comprising a pull up and a pull down transistor, the input signal to the buffer is applied to the gate of the transistors in the control circuit. The two control signals are applied to the gates of the pull up and pull down transistors of the buffer to reduce transient current. In a further improvement, where the buffer includes a second inverter including a second pull up and a second pull down transistor, two feedback paths are employed to control the gates of the two transistors in the second inverter to control the slew rate of the buffer. The passing gate of the control circuit may be turned on or off by an enabling circuit so that if the circuit is implemented in an integrated circuit having input and output pins, the control circuit can be tri-stated so that an output pin may be used as an input pin when the passing gate is disabled.

High-speed resonant-tunneling diodes made from the In0.53Ga0.47As/AlAs material system

Abstract: New double-barrier resonant-tunneling diodes have been fabricated in the pseudomorphic In0.53Ga0.47As/AlAs material system that have peak current densities exceeding 1x105 A cm-2 and peak-to-valley current ratios of approximately 10 at room temperature. One of these diodes yielded oscillations up to 125 GHz, but did not oscillate at higher frequencies because of a large device capacitance. A device with a much lower capacitance is estimated to have a maximum oscillation frequency of 932 GHz and a voltage rise time of 1.5 ps in switching from the peak bias point to the valley bias point. Other reported In0.53Ga0.47As/AlAs diodes are analyzed and yield theoretical maximum oscillation frequencies over 1 THz and rise times as low as 0.3 ps.

Light-emitting diode drive circuit with fast rise time and fall time

Abstract: A light-emitting diode drive circuit of the present invention comprises: a current supply circuit (3) including a first transistor (16), the base of which receives a first drive pulse signal (S3) output from a signal input circuit, and a second transistor (15), the collector of which is connected to a light-emitting diode (2), the emitter of which is connected to a current source (24) together with the emitter of the first transistor (16), and the base of which receives a second drive pulse signal (S2) having a phase opposite to that of the first drive pulse signal (S3); a fall time shortening circuit (6) including a third transistor (13) which is connected in parallel with the light-emitting diode (2) and the base of which receives an input for short-circuiting both terminals of the light-emitting diode (2) during a turn-OFF time; and a rise time shortening circuit (5) including a circuit (4) for generating a peaking current during a turn-ON time of the light-emitting diode (2), and a fourth transistor (14) being connected in series with the third transistor (13) and adding the peaking current to the drive current during the turn-ON time of the light-emitting diode (2), wherein rise and fall times of the light pulse output are shortened to greatly increase a response speed of the light-emitting diode (2) having poor inherent response characteristics, such as a red light-emitting diode having a short wavelength range.

Fast front-end electronics for experiments using silicon calorimeters at ssc /lhc colliders

Abstract: A fast VLSI preamplifier using HF2CMOS technology was designed and built. The preamplifier meets the requirements for silicon calorimetry application in experiments at hadron colliders SSC/LHC. The overall power consumption is less than 45 mW for a maximum output voltage swing of 5 V (≈ 7 ns rise time). The slew rate is about 700 V/μs for an input capacitance of 150 pF. The measured value of ENC (equivalent noise charge), for an RC-CR shaping time of 20 ns and an input capacitance of 150 pF, is 17 ke RMS .

Fast bistable wavelength switching characteristics in two-electrode distributed feedback laser

Abstract: Fast bistable wavelength switching between two longitudinal modes separated by 1.7 nm was achieved in a two-electrode distributed feedback laser with inhomogeneous excitation. As a result, a fast wavelength switching time less than 200 ps was observed in this device. In addition, high-speed repetitive wavelength switching operation up to 1 GHz was achieved. This indicates that the device is capable of repetitive wavelength switching within 1 ns, including delay time and rise time. >

Plasma processing equipment

Abstract: PURPOSE: To prevent the generation of abnormal voltage between a substrate and a ground part position when an RF bias voltage is applied so as to be synchronized with microwave pulses, by installing a vacuum chamber, an RF generator, etc., which constitute a plasma forming chamber. CONSTITUTION: Microwaves which are generated from a microwave source and have a rectangular envelope of ms order width are introduced into a vacuum chamber constituting a plasma forming chamber through a waveguide, and used for generating plasma. A signal for exactly monitoring the time variation of the envelope is led out from the microwave source, and delivered to a pulse generator, which is equipped with variable resistors VR1, VR2. By adjusting the resistance values of them, pulses are generated which rise up and fall down with specified delay times from the rise time and the fall time of a microwave monitoring signal. Thereby the RF pulses are applied to a substrate, only during the plasma period in an equibrium state, so that the generation of an abnormal voltage to the ground part position can be prevented, and the damage of a substrate to be treated can be prevented. COPYRIGHT: (C)1992,JPO&Japio

Gallium-arsenide charge-sensitive preamplifier for operation in a wide low-temperature range

Abstract: A charge-sensitive preamplifier for temperature operation between 1 and 120 K has been developed and evaluated. It uses double-gate GaAs MESFETs selected for their low 1/ƒ noise. These devices are operated with both gates interconnected emulating single-gate MESFETs of double gate-length, obtaining in this way a value for Aƒ, the coefficient of the 1/ƒ noise spectral power density, of 1.7 × 10−13 V2 at 77 K and 3.8 × 10−14 V2 at 4 K. The latter is one fourth the value exhibited by the original device before modification and two orders of magnitude less than the value measured at 300 K. At the optimum bias operating point device transconductance is 6 mA/V, input capacitance is less than 5 pF and the power dissipation 360 μW. The circuit configuration consists of a double-cascade loaded with a bootstrapped current source. In this way, a high gain-bandwidth product is obtained despite of the low dynamic output resistance, 3000 Ω, exhibited by the MESFETs at the operating point. Equivalent noise charge was measured for detector capacitances up to 35 pF. Using a semi-Gaussian weighting function minimum values of 58 and 20 rmse− at 77 and 4 K, respectively, were determined. Noise slopes are 4.68 and 3.64 e−/pF at 1 μs shaping time for 77 and 4 K, respectively. A rise time of 20 ns was measured at the receiving-end of a 1 m length 50 Ω coaxial cable terminated at sending-end, when detector capacitance was CD = 35 pF. The total power dissipation of the preamplifier is less than 10 mW.

Driver circuit for providing pulses having clean edges

Abstract: A method and apparatus for providing pulse signals from a driver circuit in an in-circuit overdrive/functional tester to a probe, which tester provides a control signal representative of a command for the driver circuit to provide logic signals, includes adjusting the transition time of the logic signals so that the transition time is equal to twice the time it takes the pulse signal to travel from the driver circuit to the end of the probe and back. The method or apparatus for adjusting the rise time of the control signal can include adjusting the slew rate of the control signal. Pulse signals produced by such a method or apparatus have clean edges, have slew rates which are twice as fast as the slew rates of the driver signals and have zero propagation delay when measured at the fifty percent point.

Pulsed driver circuit

Abstract: A modulator circuit provides pulses of electrical energy to an electrical load in response to a trigger signal. A normally nonconductive Mosfet is included in a series circuit path with the electrical load and a capacitor. A silicon controlled rectifier (SCR) is coupled to the gate electrode of the MOSFET. A trigger signal renders the SCR conductive to thereby render the MOSFET conductive which discharges the capacitor through the electrical load to provide a pulse of electrical energy having a rapid rise time to the electrical load. The electrical load can be a laser diode which emits a pulse of light for use in an optical ranging device in response to the pulse of electrical energy. The accuracy of the ranging device is proportional to the rise time of the pulse of light.

Low power sensing apparatus for digitizer tablets

Abstract: A digitizer tablet consuming less power than is required of current tablets comprises short duration fast rise time energizing pulses, and a resonant circuit in the induced signal detector tuned to the frequency of the pulse repetition rate or preferably a higher frequency. Peak detector or timed sample and hold circuits are connected to the resonant circuit to improve resolution and reduce noise.

A device for the determination of the microsecond component of the in vivo chlorophyll fluorescence induction kinetics

Abstract: A device for the measurement of the in vivo chlorophyll fluorescence induction kinetics at the wavelengths 685 nm and 730 nm is described. The excitation light provided by a He-Ne laser is switched by an acousto-optic modulator (Bragg cell) which achieves a rise time of the excitation light intensity Ie of 0.3 mu s. A combination with an additional mechanical shutter ensures that Ie is constant within 11% during the total measuring time of 5 min. Data acquisition is accomplished by a transient recorder with a time resolution of 10 mu s and a computer with a sampling rate adjusted between 5000 s-1 and 5 s-1. The initial fluorescence intensity F0, the inflection point Ip (during the rise of the fluorescence at the beginning), the maximum intensity Fp and the final steady-state value Fs can be evaluated with high accuracy, so additional information is provided to estimate the efficiency of the photosynthetic system.

Metalorganic gas control system for gas source molecular beam epitaxy

Abstract: We have developed a new method to precisely control the small mass flow of low vapor pressure gases without a carrier gas in gas source molecular beam epitaxy Group III metalorganic gases (TEA1, TEIn, and TEGa) were controlled by measuring the pressure difference at the flow element and giving feedback to the control valve The beam pressure of source gases monitored at the growth position in a molecular beam epitaxy growth chamber had good linearity with the pressure difference at both sides of the flow element The beam pressure was controlled with a maximum deviation of 2% for over 1 h of operation The response of the beam pressure to changes in flow rate was quick with neither overshoot nor undershoot The beam pressure could be reduced to 1/5 of its initial value in less than 5 s and then restored in less than 3 s The source gases could be switched on and off abruptly The rise time to 90% of the saturated beam pressure was less than 1 s and fall time to 10% of the saturated beam pressure was betw

On the relation between the peak frequency and the corresponding rise time of solar microwave impulsive bursts and the height dependence of magnetic fields

Abstract: In the present paper we report the results of a correlation analysis for 57 microwave impulsive bursts observed at six frequencies in which we have obtained a regression line between the peak frequency and the corresponding rise time of microwave impulsive bursts: {ie361-01} (with a correlation coefficient of - 043) This can be explained in the frame of a thermal model The magnetic field decrease with height has to be much slower than in a dipole field in order to explain the weak dependence of f p on t r This decrease of magnetic field with height in burst sources is based on the relationship between f p and t r found by assuming a thermal flare model with a collisionless conduction front

Lighting circuit of electric discharge lamp for vehicle

Abstract: PURPOSE:To quickly make the light flux of an electric discharge lamp reach the stable rated light flux thereof by operating a timer means to transfer the operational mode of the electric discharge lamp to the constant powder control mode thereof under the rated power thereof after the electric discharge lamp goes through a control operation for supplying power exceeding the rated power to the electric discharge lamp. CONSTITUTION:A lighting circuit has a control circuit 18 for generating a control signal responsive to each of output signals from both an output voltage detector circuit 29 and an output current detector circuit 34 so as to be transmitted to a d.c. voltage step-up circuit 9 and consequently controlling the output voltage of the voltage step-up circuit 9, it transmits a signal corresponding to the output voltage of the voltage step-up circuit 9 to the current detector circuit 34 after the lapse of time responsive to the lights-out time of an electric discharge lamp, and after power exceeding the rated power of the electric discharge lamp is supplied to the electric discharge lamp through a control operation specified in the order of the voltage detector circuit 29 and the current detector circuit 34, the operational mode of the electric discharge lamp is transferred to the constant power control mode thereof under the rated power by operation of a timer means. This shortens the rise time on the light flux of the electric discharge lamp while making stable constant power control of the lamp even if the load characteristic of the lighting circuit is changed due to circumferential environment or the like.

Photoconductive nanosecond pulse generation utilizing radial transmission lines

Abstract: A nanosecond, kilovolt pulse generator utilizing a radial transmission line was investigated. The device incorporates a gallium arsenide, photoconductive switch to connect the radial line to the coaxial output. Identical gridded electrodes are used on opposite sides of the switch. Switching is achieved with a 75-ps-wide pulse from a mode-locked Nd:YAG laser. In addition to the radial design, a quasi-radial structure was also investigated, in which improvements in rise time and pulsewidth were achieved at the expense of voltage gain. For the same charging voltage of 9.2 kV, the radial device delivered a 10-kV, 1.3-ns-wide pulse, while the quasi-radial device gave a 6-kV, 500-ps-wide pulse. An integrated pulser design in which the switch and the dielectric medium between conducting planes are combined into a single semi-insulating GaAs wafer is described. The potential advantages of such a device are discussed. >

4‐GHz internal MCP‐photomultiplier cross correlation

Abstract: We have performed sinusoidal and pulsed internal cross correlation within a Hamamatsu model R2024U gatable microchannel‐plate photomultiplier (MCP‐PMT) by biasing and modulating the gating mesh which is located 0.2 mm behind the photocathode. The light source used was a sync‐pumped and cavity‐dumped dye laser. Near the photocathode center, no effective high‐frequency photocurrent modulation was achieved. However, for a circular area near the photocathode edge, useful modulation up to 4.5 GHz, the frequency limit of our amplifier, was obtained. The modulation frequency response is characterized by resonances caused by the gating mesh which represents a strong disturbance with respect to the modulation‐cable termination. The shortest measured rise time for pulsed modulation was 178 ps at 700 nm. The measured pulse response is a ‘‘mirror image’’ of a response curve as observed normally because the gating pulse is sampled by the δ‐like photoelectron pulse. From this observation it can be reasoned that an even...

Output buffer circuit

Abstract: PURPOSE:To shorten a rise time to reduce the power consumption by adding a voltage auto-reset circuit to the output circuit of an output buffer circuit. CONSTITUTION:In the output buffer circuit, an output circuit 3 is provided with a voltage auto-reset circuit 2 where a nodal poin voltage VN of a nodal point N is inputted to a gate GP3 and the source receives supply of a source supply voltage VSS of the earth point and the drain is connected to an output terminal T0. Consequently, this output buffer circuit performs the source follower operation at the time of operating in a steady state, and the function to drive a capacitive load CL is improved by a field effect transistor QP3 connected in parallel with a constant current source at the time of switching for failing. Thus, the power consumption of the output buffer circuit is reduced.

Harmonic-generation experiments on the Mark III free electron laser

Abstract: An understanding of the harmonic-emission process in an FEL oscillator is important so that the properties of the harmonic emission can be tailored for maximum usefulness. In scientific applications one might wish to minimize the bandwidth of the harmonic radiation, while in high-powered FEL oscillators one might wish to minimize the energy in a particular harmonic to avoid mirror damage. In previous work we showed that the bundwidths of the harmonics are considerably larger than predicted by simple theory. Numerical simulation of the harmonic emission process has led to a better understanding of the bandwidths. As the fundamental power changes during a micropulse, the harmonics go through multiple cycles of bunching and overbunching, leading to multiple peaks in the harmonic micropulse and spectral broadening. This oscillatory dependence of harmonic power on instantaneous fundamental power has also been predicted elsewhere for the optical klystrom. In addition to our bandwidth measurements, we have measured spatial profiles, small-signal rise times, and ratios of coherent/incoherent harmonic emission. The small-signal rise time for the nth harmonic (n = 4−6) is a factor of n smaller than the fundamental rise time, as theory predicts.

Vibration-sensitive intrusion detection system

Abstract: An intrusion detection system for detecting attempts to penetrate a vertical barrier such as a fence or wall includes a strain sensitive cable 10 which generates an alarm signal in response to movement of the barrier. The alarm signal is amplified 12 and filtered 14 and passed to a detector circuit 16 when it is rectified and converted to an envelope signal characteristic of the time taken for the alarm signal to rise from zero to its peak value (the rise time). The envelope signal is differentiated 26 to remove slow rise time signals and then supplied to a threshold detector 32. Signals which exceed the pre-set threshold value are counted 34 as to their frequency in a pre-set time period determined by a timer 36. Repeated signals in excess of the threshold value lead to activation of an alarm circuit 38 as being indicative of an intrusion. Any long term continuous signal generated by the cable 10 is detected by a second threshold detector 44 which will also activate the alarm circuit 38 if the signal persists for longer than a pre-determined period measured by a timer 46.

A reduced capacitance concept for high-speed optical position-sensitive devices (PSDs)

Abstract: Position-sensitive devices (PSDs) in which the junction capacitance is reduced by using a mesh-type resistive layer with 125- mu m pitch and 30- mu m stripwidth are discussed. The temporal responses to pulsed excitation illuminated at the center are characterized by a rise time of less than 550 ns, which is shorter than that of the conventional type. The 14-mm*14-mm PSD has a junction capacitance of less than 180 pF, which is estimated to be lower than that of a conventional-type PSD by a factor of 2.4. By suitably selecting the mesh pitch and width, it is possible to reduce the temporal response by one or two orders of magnitude. >

High voltage driver for gas discharge lamps

Abstract: A pulse driver circuit for providing very high frequency pulses with fast rise time to neon or gas discharge lamps to thereby produce higher optical output than is possible using conventional drivers Gas discharge lamps have at least two states of operation One is the application of breakover voltage to initiate gas ionization which may be called the preionization state The second state is known as the breakdown condition which is when the gas in the lamp has ionized and is producing the optical output The pulse driver, starts the ionization at a relatively low breakover voltage because of its fast rise time The pulse driver comprises an astable oscillator, the output of which passes through a pulse width capacitor The generated pulse train drives a power driver transistor which causes current to flow through a transformer causing a voltage to be applied to a lamp The power applied to the transformer is used in a feedback loop which provides pulse width control to keep the current applied to the transformer constant so that the output of the lamp is relatively constant over a given voltage range