Minimum pulse width

Many switcher ICs are in fact designed with a certain minimum on-time (especially the current mode control types). They also keep to the minimum pulse width until about 0.2 to 0.3V on the feedback pin. In such cases, with a reasonably large output bulk capacitor, you will see a huge inrush of current into the output capacitor, even before the latter starts to rise appreciably. You should also be aware that inrush current into the input capacitor of any topology is very high, and no switch action can even hope to prevent that. 

The minimum pulse width delivered by a PIN or avalanehe photodiode is given by the produet of the junetion eapacitance, Cj, and the load resistance of 50 Ohm. A small Cj is aehieved only if the 1 region of a PIN diode or the avalanche region of an APD is fully depleted. This requires PIN diodes to be operated close to their maximum permissible reverse voltage. APDs should be used at 30% or more of their breakdown voltage. 

A similar laser, with diode end-pumping, could produce pulses of 128 ns at a repetition rate of 230 kHz, with a slope efficiency of 9 % [151, 152]. One of the examples was a LD-end-pumped passively g-switched Nd YAG ceramic laser, operated at 1319 nm with a V YAG saturable absorber [151]. An average output power of 1.8 W was achieved at the pump power of 23.7 W, which corresponded to an optical conversion efficiency of 7.8 % and a slope efficiency of 9 %. The minimum pulse width of 128 ns at a pulse repetition rate of 230 kHz was obtained with a T = 2.8 % OC at the pump power of 23.7 W. Another example was a side-pumped Nd-doped Gd(0.6)Y(0.4)VO(4) bounce laser, which was combined with a V YAG saturable absorber crystal [152]. It offered a passively g-switched output of 6.5 W at 1.3 pm. Output powers of 6.5 and 6 W were observed at a maximum pump level for the multi- and TEM(00)-mode operations, demonstrating optical-to-optical efficiencies of 17.5 and 16.2 %, respectively. 

Second, for a particular system and yield, there is some minimum pulse width required (minimum impulse for a given pressure) to bring the necessary amount of coolant to the melt. Both of these requirements can be described by an equation of the form ... 

If the trim will plug, use pulse width modulation and set the ratio of the maximum to minimum pulse width to achieve the desired rangeability. 

Although the correction to ray transit time due to fiber nonuniformities is small, we recall from Chapter 3 that the pulse width on a weakly guiding fiber is also small. For example, the minimum pulse width of Eq. (3-9) for the optimum clad power-law profile is proportional to A, or 6. We investigated the effect of material dispersion on pulse spreading in Section 3-8 here we account for the effect of slight nonuniformities on the pulse minimum. 

We showed in Section 3-2 that the minimum pulse width on a uniform fiber with a clad power-law profile is acutely sensitive to small changes in exponent about the optimum profile. The effect of exponent nonuniformities on the optimum profile can be deduced by substituting of Eq. (3-8) into Eq. (5-36). Since the fiber is assumed weakly guiding, the effective exponent is... 

W.m (see Ch.l4). To get enough return flux at the minimum laser power, one needs to optimize the laser specifications (continuous wave or pulsed, pulse width, pulse repetition rate, (average) power, spectral profile) taking into both saturation, technological, budget and operation constraints. This is the challenge described in detail in the above mentioned chapter. 

To carry out a spectroscopy, that is the structural and dynamical determination, of elementary processes in real time at a molecular level necessitates the application of laser pulses with durations of tens, or at most hundreds, of femtoseconds to resolve in time the molecular motions. Sub-100 fs laser pulses were realised for the first time from a colliding-pulse mode-locked dye laser in the early 1980s at AT T Bell Laboratories by Shank and coworkers by 1987 these researchers had succeeded in producing record-breaking pulses as short as 6fs by optical pulse compression of the output of mode-locked dye laser. In the decade since 1987 there has only been a slight improvement in the minimum possible pulse width, but there have been truly major developments in the ease of generating and characterising ultrashort laser pulses. 

MINIMUM C3 = 680 pF LESS WONT TRIGGER OJOOl CAUSES ERRATIC PULSE WIDTH ADJ. AT 80 uS OF 250 uS MAX. [ C4 = 0J005 F ... 

The laser used to generate the pump and probe pulses must have appropriate characteristics in both the time and the frequency domains as well as suitable pulse power and repetition rates. The time and frequency domains are related through the Fourier transform relationship that hmits the shortness of the laser pulse time duration and the spectral resolution in reciprocal centimeters. The limitation has its basis in the Heisenberg uncertainty principle. The shorter pulse that has better time resolution has a broader band of wavelengths associated with it, and therefore a poorer spectral resolution. For a 1-ps, sech -shaped pulse, the minimum spectral width is 10.5 cm. The pulse width cannot be <10 ps for a spectral resolution of 1 cm . An optimal choice of time duration and spectral bandwidth are 3.2 ps and 3.5 cm. The pump pulse typically is in the UV region. The probe pulse may also be in the UV region if the signal/noise enhancements of resonance Raman... 

The parameters that will be measured in each of the software packages and the hardware are the minimum and maximum voltages, the rise and fall time of the output, and the effective pulse width. The response of the IsSpice model is shown as Fig. 3.32. Micro-Cap results are shown as Fig. 3.33. PSpice results are displayed in Fig. 3.34, and the hardware measurements are shown as Fig. 3.35. 

The usefulness of constructing the function CM + t(z, x) arises from the theorem20,22 that as t varies over the real axis, CM+1(z, t) varies over a circle in the complex plane. For all possible nonnegative densities I(co) having the specified moments, J(z) must fall within or on this circle.20,22 Thus we may determine the minimum and maximum possible values of I(Z0,e) using Eq. (19), from the minimum and maximum imaginary parts of these circles.23 The upper and lower bounds to I(co0,0 may be evaluated recursively from a for any given values of frequency co0 and pulse width . 

TOFSIMS analyses were performed on a Kratos PRISM instrument. It was equipped with a reflectron-type time-of-flight mass analyzer and a pulsed 25 kV liquid metal ion source of monoisotopic 69Ga ions with a minimum beam size of 500 A. Positive and negative spectra were obtained at a primary energy of 25 keV, a pulse width of 10-50 ns, and a total integrated ion dose of about 10" ions/cm2. This is well below the generally accepted upper limit of 5 x 1012 ions/cm2 for static SIMS conditions in the analysis of organic materials [12], The mass resolution at mass 50 amu varied from M/AM= 1000 at 50 ns pulse width to about 2500 at 10 ns pulse width. 

The current pulse from a single photon event would be noted at the anode as an approximate million electrons and a pulse width in nanoseconds. The amplifier changes the anode current pulse into a pair of voltage signals with sufficient gain and output impedance to couple it to the discriminator, which then shapes the pulse and rejects those below a set minimum threshold. The maximum count rate of less than lO pulses/s determined by the pulse pair resolution of the amplifier-... 

Combination of a pulsed bias and noncontact AFM has been found to improve the control of the writing process [78]. This method reduces the tip-substrate interaction time and thus improves the reliability and lithographic resolution. The frequency of oscillation and the field pulsing frequencies need to be adjusted to create a definite phase relation between the two and it was found that the minimum line width is obtained when the applied field is on during the time the cantilever tip is furthest from the substrate. The process also needs adjustment of the duty cycle. 

Comparison of initiation-threshold measurements suggests that there is a minimum thickness, or a run-up distance, before detonation occurs and that this is independent of pulse-width for stresses up to 10 kbars. For long pulses (3.5 psec) in the gas gun, no evidence of detonation was detected for 1-mm-fhick samples. Detonation occurred with run-up distances in the range of 1-2 mm for impact stresses of 8.9 kbar. For stresses greater than 6.0 kbar, evidence of detonation was noted after a 2-mm run. In the thin-flyer-plate experiments at stresses of 8 kbar, dextrinated lead azide displayed a 2-usec initiation delay. Voreck and coworkers [8] determined that a similar minimum thickness of lead azide is required for complete detonation in an explosive train consisting of NOL-130, lead azide, and RDX (Figure 15). 

Estimate the minimum 90° pulse width you would need to excite peaks in this complete range to within 90% of the their theoretical maximum for a spectrometer with a Bq field strength of 9.4 T. 

---