Multiplication in collector junctions of silicon n-p-n and p-n-p transistors

The values 1-1/Mfor both electrons and holes, whereMis the multiplication factor, have been calculated in three different silicon p-n junctions. The logarithmic plot of 1 - 1/Mversus the normalized voltageV/V_{B}is well approximated by a straight line for 0.1 > 1 -1/M> 0.005. This range corresponds to the useful range of α0for most bipolar transistors. An empirical expression has been obtained for the ratioV_{CEO}/V_{CBO}within this range.     

Reliability of circular consecutively-connected systems withmultistate components

A circular consecutively-connected system with multistate components (CCCSMC) consists of a set of a components e_i, i∈[1,n] arranged in a circle. The e_i is followed by e _i+1, i∈[1,n-1]; e_n is followed by e₁ . The e_i can be in 1 of the states 0,…,k_i . If e_i is in state k∈[0,k_i], then its range is k (the k components following e_i are within its range). The system is functioning if and only if, for every component e _j, j∈[1,n] there is an e_i such that e_j is within the range of e_i. The paper gives a recursive algorithm for determining the CCCSMC reliability     

Effect of dislocations on 1/f noise of long wavelength infrared photodiodes fabricated with HgCdTe layers grown on GaAs by metalorganic vapor phase epitaxy

We studied the effect of dislocations on the 1/f noise current of long wavelength infrared photodiodes fabricated with HgCdTe layers grown on GaAs by metalorganic vapor phase epitaxy. N-on-p junctions were formed by boron ion implantation into Hg-vacancy doped epilayers. The 1/f noise dominated from 0.5 to 100 Hz, and shot noise caused by photocurrent (√2eI_p) dominated at higher frequencies. We observed two types of 1/f noise. One is caused by the leakage current generated at dislocations, and the other is induced by the photocurrent. The 1/f noise current increased with the photon flux in the low-etch pit density (EPD) range independently of EPD. It increased with EPD in the high-EPD range. The 1/f noise current measured at zero field of view increased with EPD. This suggests that the 1/f noise generated by the photocurrent dominated in the low-EPD range, and that the 1/f noise current caused by dislocations dominated in the high-EPD range. In order to obtain a thermal image of a room-temperature object, the 1/f noise current induced by background photon flux is as high as that caused by dislocations of more than 10⁷ cm⁻². Therefore, the 1/f noise current induced by the photocurrent is dominant in photodiodes fabricated with HgCdTe layers on GaAs, since the EPD is less than 2 x 10⁶ cm⁻². We expect the detectivity to be as high as with LPE-layers. We fabricated 64 x 64 photodiode arrays, and obtained a thermal image.     

Development of prototype fiber-optic-based Fizeau pressure sensorswith temperature compensation and signal recovery by coherence reading

A range of prototype fiber-optic-based Fizeau interferometric pressure sensors with temperature compensation and signal recovery by dual-wavelength coherence reading have been developed. A separate fiber-optic-based Fizeau temperature sensor with similar cavity length was incorporated into the pressure sensor to allow the pressure measurement to be corrected for the temperature dependence of the pressure probe. The pressure and temperature probes were multiplexed spatially. For the low-pressure sensor, the obtained range to resolution ratio and the accuracy were ~6.7×10³:1 and better than ±1 percent over a pressure range of 0-0.48 bar, respectively. For the medium pressure sensor, the achieved range to resolution ratio and the overall accuracy were 3.6×10⁴:1 and ±0.15 percent over a full-pressure range of ~10 bar. For the high pressure sensor, a range to resolute ratio of ~1.67×10⁴:1 and an overall measurement accuracy of ±0.69 percent over a pressure range of ~1000 bar have been achieved. Due to the universality of the signal-processing scheme based on the dual-wavelength coherence-reading technique, the signal-processing box can be compatible with a range of sensors illuminated by the sources with similar central wavelengths. This study would be readily used to develop a range of commercial fiber-optic pressure sensors with similar optical path differences, interrogated by a universal signal-processing box, for different applications     

Electrical characterization of interface states in Ni/n-Si(111) Schottky diodes from (C-V) characteristics

Experiments have been performed on Ni/n-Si(111) Schottky diodes fabricated by the vacuum vapor deposition of Ni at 10⁻⁵ Torr pressure on an n-type «111å oriented silicon wafer. Measured current-voltage and capacitance-voltage characteristics in range frequency range 10 kHz-1 MHz have been analysed. Interface states parameters have been extracted from (C-V) characteristics using a metal-thin interfacial layer-semiconduct (MIS) structure model. The interface states density has been found to be in the range of 10¹¹ cm⁻² eV⁻¹ with a peak in the band gap of Si at about 0·51 eV below the conduction band edge.     

Impact of noise of linearity of SQUID feedback loops at high slewrate

A simplified digital DC SQUID (superconducting quantum interference device) system has been simulated to determine the degree of linearity in a digital flux-locked-loop (FLL), with 12-b D/A converter. The influence of comparator noise and quantization noise on the feedback loops corresponding to single- and two-pole integrators is investigated as a function of the normalized slew rate s_N =s/s_max. A simple approximation describing the attainable linearity up to a specific slew rate range is suggested. Measurements with and without a DC SQUID magnetometer in a digital FLL system yielded a satisfying agreement with simulations in the range 0.3<s_n⩽1     

ISDN loop extension using a mid span amplifier

The 5·5 km range of the basic rate ISDN loop has been extended by using a negative impedance amplifier and by using a 2 wire/4 wire (2w/4w) amplifier. The negative impedance amplifier extends the range of the loop by 1·0 km, whereas the 2w/4w amplifier extends the range by 1·5 km at the expense of increased complexity. As part of the amplifer design, a resistor/capacitor network has been developed which closely matches the characteristic impedance of telephone cable. Error rate tests have been conducted using various lengths of cable and an operating ISDN line.     

Single grating period quantum cascade laser array with broad wavelength tuning range

A distributed feedback quantum cascade laser array emitting at λ∼ is reported. Utilising a ridge width dependence on emission wavelength, the array of laser ridges exhibited a tuning range in excess of 230 nm over the temperature range of 140 to 380 K. Singlemode operation with sidemode suppression ratios of / spl ges/25 dB and a combined tuning coefficient of -0.1 cm^-1 K^-1 are demonstrated.     

40-wavelength rapidly digitally tunable laser

We present a tunable laser based on an N₁×N₂ chirped waveguide grating router that has N₁N₂ wavelengths, accessible in a digitally rapid manner, and only N ₁+N₂+1 semiconductor optical amplifiers. By using chirp, the free-spectral range of the router can be significantly less than the channel span. The version demonstrated here has N₁=5, N₂=8, a channel spacing of 100 GHz, and the router free-spectral range is only 20 channels     

Efficient difference frequency oscillator based on a Ti:sapphirelaser

The problem of expanding the Ti:sapphire laser wavelength range by generating difference (sum) frequencies is discussed. The authors present a high-efficiency coherent radiation source, based on a Ti:sapphire laser and a nonlinear LiIO₃ crystal, operating in the spectral range from 0.34 to 2.3 μm. For this purpose a Ti:sapphire dual-wavelength laser has been developed where the process of self-synchronization of both channels has been realized. A difference frequency oscillator with 2w_s-2w_l and 2w_l-w _s, including the spectral range from 0.503 to 0.79 and from 0.83 to 2.3 μm, has been realized. A detailed study of the temporal characteristics of Ti:sapphire lasing is given, the development of methods for mixed pulse overlapping is discussed, and other subjects, such as configuration of widely tunable coherent radiation sources, are addressed     

MOSFET-C filter, with low excess noise and accurate automatictuning

Continuous-time integrated filters having a maximum dynamic range at the audio-frequency range are obtained using MOSFET-C filters. Using MOSFET-C filters in combination with a well-designed BiCMOS amplifier, the detrimental influence of 1/f noise can practically be eliminated and the filter noise is completely determined by the unavoidable thermal noise of the filter resistors. A 98-dB dynamic range (total harmonic distortion<0.3%) is obtained in a fifth-order Butterworth low-pass filter, while the overall 1/f noise corner frequency is limited to 250 Hz. Automatic adjustment of the filter cutoff frequency is performed using a novel all-silicon automatic tuning system that, compared with traditional automatic tuning systems, has reduced overhead circuitry     

A Modular Phase-Frequency Detector Design with ±2nπ Linear Range of Operation

To extend the linearity range of the phase-frequency detector/charge pump (PFD/CP) circuit, a modular design for a novel PFD architecture is proposed. The new circuit yields a modular extension range of –2N to 2N, where N is an integer representing the order of the PFD/CP extension. The efficacy of the new PFD/CP is demonstrated by the improved frequency acquisition time obtained via closed-loop simulation. Hence, the developed architecture is a good candidate for phase-locked loops requiring the use of PFD/CP with a broad linear range of operation.     

Comments on `A compact thermal noise model for the investigation ofsoft error rates in MOS VLSI digital circuits'

For the original article see ibid., vol.24, no.1, p.78-89 (1989). In the above-title paper by P.D. Layman and S.G. Chamberlain, the mean-square noise voltage of a MOSFET transistor was determined in the frequency range Δf=2.2/(2πt_sen)=0.35(1/t _sen), whereas the mean-square value (and consequently the RMS) of thermal noise in the RC circuit was determined over an infinite frequency range. The commenter examines the implications of this approach to draw attention to a few questions that can significantly influence the accuracy of results in the course of consideration of noise in electronic circuits     

The relation between range sampling rate, system bandwidth, andvariance reduction in spectral averaging for meteorological radar

Periodograms are frequently used in radar meteorology to get spectral moments of weather echo. Each range trace is sampled and the set of samples at each of the specific ranges is used to obtain a pulse-to-pulse periodogram from which the spectral moments are estimated. Over some range interval, the separate periodograms would be averaged to get smoother estimates to be reported. The averaging will reduce the variance of the spectral estimates but the resulting variance is not quite inversely proportional to the number of periodograms because of the correlation introduced by a sampling rate that preserves range resolution. The authors derive the equivalent number M_eq of uncorrelated range-samples when M range samples are actually averaged. The factors involved are the 3-dB system half-bandwidth W, the number M, and the range sampling frequency f_s . The formula is M_eq=M[1+2Σ(_r=1)^M-1 (1-r/M)exp(-28.48r²W²/f_s² )]^-1. A table is provided of M_eq versus M     

An analytical model for the determination of optimal outputreflectivity and fiber length in erbium-doped fiber lasers

An analysis relating the output power of erbium-doped fiber lasers to the output mirror reflectivity r_out is performed, and a closed-form expression valid for r_out<0.95 is obtained. It shows that the laser output power is nearly independent of the output reflectivity when 0.5<r_out<0.95. The closed-form expression is used to study the dependence of the output power with laser wavelength and confirms the large tuning range (60 nm) already reported. However, it is shown that the tuning range is greatly increased (up to more than 100 nm) if r_out is chosen near 0.9. Finally, an approximate expression for the optimal fiber length needed to achieve maximum laser output is derived     

Analysis of the threshold voltage and its temperature dependence in electrolyte-insulator-semiconductor field-effect transistors (EISFET's)

A first-order theoretical model is developed that allows the temperature dependence of the threshold voltage of an electrolyte-insulator-semiconductor field-effect transistor (EISFET) to be determined. Specifically, a detailed analysis is presented for a representative cell consisting of a Ag/AgCI reference electrode, a simple 1:1 electrolyte, and an ISFET. In addition, an insulator is assumed for which the site-binding model is applicable. All temperature-dependent parameters are identified and quantitatively described. Results are computed for SiO2and Al2O3insulators over a pH range from 1 to 12, and a temperature range from 20 to 80°C. Graphs of the surface-site occupancies versus the pH are shown to provide useful physical insight in interpreting the results. The threshold-voltage temperature coefficient is shown to be highly dependent on the pH; however, for Al2O3, over a 20-80°C range, the variation is roughly linear.     

Distributed Bragg-reflector Pb1-xSnxTe/PbSeyTe1-ydiode lasers

Distributed Bragg-reflector (DBR) diode lasers were designed and fabricated from lattice-matched Pb1-xSnxTe/PbSeyTe1-ysingle heterostructures grown by liquid-phase epitaxy. These DBR lasers operated in a single longitudinal mode within a limited range of heat-sink temperatures, 8.5-38 K, with a threshold current density of ∼3 kA/cm²at 20 K. Single longitudinal mode operation was maintained up to more than three times the threshold current. Continuous tuning of the laser output frequency over a range of ∼6 cm^-1, near 775 cm^-1(12.9 μm), was acheived by varying the heat-sink temperature. The average tuning rate was 0.21 cm^-1/K, and it was much smaller than the rate for corresponding Fabry-Perot lasers, which was 2.3 cm^-1/K. The measured effective mode index of the DBR lasers agrees well with the calculated one.     

Simplified approach to assessing intravenous flow characteristicsin the therapeutic infusion range

It is shown that the pressure-flow (P-F) relationship in intravenous infusion systems can be simply described by the flow parameters R_L (linear-resistance) and F_E (flow nonlinearity). The relative-pressure error due to nonlinear flow is found to be insignificant in the flow range used for therapeutic intravenous infusion therapy (F⩽300 ml/h); a linear P-F model would therefore suffice. At higher flows such as 999 ml/h and in the fluid resuscitation range, the nonlinear contribution to the P-F relationship becomes significant     

Reduction of channel hot-electron-generated substrate current insub-150-nm channel length Si MOSFET's

Channel hot-electron-generated substrate currents were measured in MOSFET devices with channel lengths down to 0.09 μm, and a family of characteristic plots of substrate current, normalized to drain current, I_SUB/I_D, rather than (V _DS-V_DSAT)^-1 was obtained. For channel lengths greater than 0.5 μm, the characteristics are independent of channel length. For channel lengths in the range of 0.15 μm, the characteristics are independent of channel length. For channel lengths in the range of 0.15 μm, the normalized substrate current at constant V_DS increases with decreasing channel length. However, as the channel length is decreased below 0.15 μm, a decrease of the normalized substrate current is observed. The decrease is larger at 77 K than at 300 K. This decrease accompanies the onset of electron velocity overshoot over a large portion of the channel. It is suggested that the decrease is due either to a decrease of carrier energy because energy relaxation and transit times become comparable, to a relative decrease of the carrier population in the channel, or to both     

A balanced 0.9-μm CMOS transconductance-C filtertunable over the VHF range

A balanced transconductance-C biquad implemented in the digital subset of a 0.9-μm CMOS process operates at frequencies up to 450 MHz and Q factors from a nominal value near 1 to approximately 100 with 30-40-dB dynamic range. By switching in capacitors and adjusting control voltages it can be tuned to below 30 MHz, demonstrating the capability of operating over the entire VHF range. Active area is 0.029 mm² and power consumption is 8-12 mW with a 5-V power supply