共查询到20条相似文献,搜索用时 15 毫秒
1.
《Electron Devices, IEEE Transactions on》1984,31(10):1408-1413
The predominant noise is1/f noise and consists of two parts: a) Noise varying asImin{C}max{2} , generated mostly with conducting channel and predominating for normal values of the collector voltage VCE . b) Noise at low VCE and practically independent of VCE ; it is generated chiefly in the space charge region around the base grating and gives collector1/f noise atV_{CE} = 0 . The turnover frequency of the first noise source lies at about 20 MHz forV_{CE} = 0.30 V,V_{BE} = 0.20 V. At sufficiently high frequencies the PBT shows thermal noise of the output conductanceg_{c0} at zero bias. Generation-recombination noise is observed at large VBE and low VCE and comes mostly from the space charge region around the base grating. 相似文献
2.
《Electron Devices, IEEE Transactions on》1967,14(12):808-816
It is shown that the observed values of the minimum noise figureF_{min} of UHF transistors in common base connection can be explained in terms of the device parameter(1-alpha_{dc}) r_{b'b}/R_{e0} and fα for frequencies up to 1000 MHz. An interesting collector saturation effect is observed that gives a strong increase in UHF noise figure at high currents. Many features of the dependance ofF_{min} on operating conditions can be explained by this effect. The current dependence ofF_{min} for large values of |VCB | and high currents suggests a distribution in diffusion times through the base region. At intermediate frequencies, the noise figure increases with increasing collector bias |VCB | due to an increase inr_{b'b} , which in turn is caused by the dependence of the base width on |VCB |. 相似文献
3.
《Electron Devices, IEEE Transactions on》1957,4(1):6-14
The effect of collector depletion layer capacity on the transient response of junction transistors to a current input is calculated for the case of a resistive load. Expressions are given for the small-signal rise-time of the common-base, emitter, and collector configurations and for the large-signal turn-on and decay times of the common-emitter and collector configurations. The analysis shows that the transient durations under most conditions of operation are approximately (1 + omega_{alpha}R_{L}C_{c} ) times those which would be predicted for the short-circuit output approximation reported by Moll [1]. Experimental results are reported which exhibit an excellent agreement with the analysis over a wide range ofomega_{alpha}R_{L}C_{c} . An empirical examination has been made of the dependence of large-signal switching time on the range of operating point excursion. A satisfactory approximate representation of this dependence is provided by a first-order correction factor, which takes into account the functional dependence of ωα and Cc on collector voltage. 相似文献
4.
《Electron Devices, IEEE Transactions on》1968,15(2):125-128
This paper deals with the second breakdown of transistors with epitaxial collector, epitaxial base, and diffused emitter. Transistors were fabricated with base width WB in the range of 2 to 18 µ and resistivity in the range of 0.1 to 10 ohm . cm. The optimum values of the resistivity and the thickness of these regions were calculated by computer techniques. The devices were mounted onto a TO-63 header and the base and the emitter leads were bonded onto the device ultrasonically. The electrical characteristics, including the frequency response ft and secondary breakdownS/B capability, were tested. For the measurement of second breakdown current IM , forward bias condition was used. It was found that for fixed collector and emitter parameters, IM was controlled by the product of base resistivity ρB and base width WB . The value of IM was found to increase withrho_{B}W_{B} . However, for a specified device characteristic, an optimum value ofrho_{B}W_{B} was found to exist. For transistors withV_{CEO} =150 volts,f_{t}=20 mHz andh_{FE}=20 , the optimum value ofrho_{B}W_{B} was found to be 6 × 10-4ohm . cm2. 相似文献
5.
《Electron Devices, IEEE Transactions on》1958,5(3):127-130
The diffused-base transistor structure affords a degree of design flexibility not found in previous structures. This is true because it has a larger number of independently adjustable design parameters than the previous structures. Its flexibility has been exploited in an oscillator transistor for 200-mc service. Design analysis shows that low ohmic base resistance, low collector body resistance, and operation at about 0.3 of the collector breakdown voltage are desirable in the present application. The methods of Lee have been used in making this germaniump-n-p diffused-base unit. Alloyed emitter and base electrodes are parallel stripes approximately 0.5-mil apart, each measuring 1 × 6 mils. The collector is about 4.5 × 8 mils. Typical parameters at Vc = -10 volts and 1E = 10 ma are: fα = 600 mc,r'_{b} = 35 ohms, and Cc = 1.0 mmf. Median 200-mc oscillator efficiency of 50 per cent is obtained at the design bias point of -20 volts, 10 ma; this exceeds the performance objective. The unit withstands 20,000-g accelerations in any direction, an additional demand imposed by the specific application for which it was developed. 相似文献
6.
《Electron Devices, IEEE Transactions on》1973,20(7):642-647
The influence of As surface concentration CSE on the emitter efficiency βγ and the temperature dependence of βγ are reported. The theoretical model that is used to explain the variation of βγ with CSE is based upon the difference in the effective energy bandgaps in the emitter and base regionsDeltaE_{g} . Experimental measurements ofDeltaE_{g} versus CSE are presented. Measurements of βγ versus CSE show that the effective emitter doping densityQ_{E}/x_{eb} reaches a maximum value atC_{SE} cong 1.5 times 10^{20} atoms/cm3, corresponding to the threshold above whichDeltaE_{g} > 0 . For the case of a constant active base doping/cm2QB , this also corresponds to an optimum in the emitter efficiency βγ . However, it is shown that in typical sequential diffusion processing of transistors, βγ increases monotonically with CSE becauseQ_{B} = Q_{B}(C_{SE}) decreases. In addition, for devices fabricated in this study,Deltabeta_{gamma}/DeltaC_{SE} atC_{SE}=2 times 10^{20} atoms/ cm3for As-diffused emitters (doped oxide) was ≈ 5 times greater than for ion-implanted-diffused As emitters, showing the superiority of implantation in controlling gain. Finally, transistors that were made withC_{SE} siml 1.4 times 10^{20} atoms/cm3(DeltaE_{g} = 0 ) showed βgamma (85°C)/ βγ (-15°C) ≤ 1.05. 相似文献
7.
《Electron Devices, IEEE Transactions on》1963,10(3):120-133
By treating the Silicon Controlled Rectifier as a hook transistor and measuring its current amplification factor as a function of frequency, the small-signal low-frequency alphasalpha_{n0} andalpha_{p0} of the n-p-n and p-n-p transistor sections constituting the Controlled Rectifier can be separately determined, together with fn and fp , their respective cutoff frequencies. Repeating these measurements at a number of bias currents, coupled with a numerical integration, enables one to separate the component dc currents of the two transistor sections as well as their dc alphas αn and αP . Measurements indicate that switching from high to low impedance is controlled byalpha_{n0} + alpha_{p0} = 1 and notalpha_{n} + alpha_{p} = 1 as has hitherto been implied. There are good theoretical reasons for this which have led to a redefinition of the breakover conditions. These are shown to be given by infinite output admittance and not infinite current as has so far been thought to be the case.alpha_{n0} andalpha_{p0} were also measured and plotted as a function of voltage bias. 相似文献
8.
《Electron Devices, IEEE Transactions on》1986,33(3):391-401
Distributed series resistance effects in solar cells are analyzed and the correctness of representing these by a lumped parameter is discussed for any conditions of bias and illumination. In addition to a general mathematical methodology, analytical expressions are derived to simplify the estimation of series resistance effects on the dark and illuminatedJ-V characteristics of the cell. The equivalent series resistance (rs ) in the dark is found to decrease with current densityJ fromr_{b} + r_{e}/3 at smallJ to (r_{e} r_{b})^{1/2} at very highJ , where re and rb are the emitter layer and base region resistances, respectively. For illuminated conditions rs depends onJ as well, being maximum near short-circuit and minimum near open-circuit; however, rs further depends on the photogenerated current JL : its short-circuit value increases with JL fromr_{b} + r_{e}/3 tor_{b} + r_{e}/2 and the open-circuit value decreases with JL fromr_{b} + r_{e}/3 to(r_{e}r_{b})^{1/2} . The variability of rs is therefore related to the relative importance of rb andr_{e};r_{b} plays the role of attenuating this variability, a situation not well recognized previously. Previous theoretical and experimental work is critically reviewed throughout this paper. 相似文献
9.
Based on the recently determined Rydberg series of the3Sigma+_{u} excimer states of Ne*2 , Ar*2 and Kr*2 , the photoionization cross sections of these molecules are calculated using a single-channel quantum defect method. These cross sections are found to differ considerably from those of the asymptotic metastable atomic Rg*(ns^{3}P_{2} ) states, but are in good agreement with recently reported experiments at isolated wavelengths. The implications of these results for VUV and XUV lasers are discussed. 相似文献
10.
A single unfocused pulse of a free running CO2 laser, area ∼ 8 cm2, initiates an explosive reaction between SF6 and SiH4 . This occurs at a minimum energy of 4 J [full width at half maximum (FWHM)sim 1.5 /mu s] of which about one half is absorbed in an 8 cm long cell; total pressure 12 torr; 0.65 <p (SiH4 )/p (SF6 ) < 1.8. The spectral and temporal distributions of the emitted chemiluminescence depend sensitively on the fuel to oxidizer ratio, and on the pulse energy; we investigated the range 4 → 20 J. The principal emission is due to S2 (B^{3}Sigma-_{u} rightarrow X^{3}Sigma-_{g} ). Transitionsupsilon' (0-4) rightarrow upsilon" (2-15) were recorded. In the3Sigma-_{u} state, vibrational temperatures range from 3000-13000 K. The luminosity peaks sharply at (SiH4 )/(SF6 ) = 1.0 ± 0.05. On each side of the maximum of the emission versus composition curve [at (SiH4 )/(SF6 ) ≈ 0.95 and 1.22, for a 12 J pulse] the residual SF6 (0.2-0.5 percent of initial amount) is enriched in34SF6 ; the observed fractionation factors at these two compositions are 8 ± 2. The separation between the two sharply peaked optimum compositions appears to increase with increasing pulse energy. Preliminary results with other fuels suggest that the concurrent absorption of CO2 laser radiation by the fuel, as well as a highly exothermic reaction, are pre-requisite for fine tuning of composition, injected power, and total pressure for optimum isotope fractionation. 相似文献
11.
Starting with a perturbation expansion for the Kleinman forbidden nonlinear optical coefficientd_{ijk^{F}} and for Miller'sDelta_{ijk^{F}} , and making several approximations, we arrive at a simple result for the ratio of forbidden to allowed mixing nonlinearities (omega_{1} + omega_{2} = omega_{3} ), namelyDelta_{ijk^{F}}/Delta_{ijk^{A}} propto (omega_{3}^{2} + 2omega_{1}omega_{2}) . For second-harmonic generation (SHG) this can be expressed asDelta_{ijk^{F}}/Delta_{ijk^{A}} simeq (omega/chi)(partialchi/partialomega) , which clearly shows the close connection betweenDelta_{ijk^{F}} and the linear dispersion. These expressions are shown to give good agreement with literature experimental values, as well as for our measurements on TeO2 for various input frequencies ω1 and ω2 (i.e.,omega_{3} = 1.88, 2.33, 2.82, 3.50 , and 3.76 eV). 相似文献
12.
A transverse, multiple-arc pulsed discharge has produced laser emission in NF3 and N2 F4 mixed with H2 , CH4 , C2 H6 , HCl, HBr, and natural gas.P_{10}, P_{21}, P_{32} , and P43 HF transitions were observed. The peak powers measured ranged from ∼8.5 to 25 kW with typical pulsewidths ofsim0.3 mu s. 相似文献
13.
This paper indicates both experimentally and graphically how the distribution of carriers changes above a critical temperature Tc , which is related to the density of states ρ in the band tails. Thus,kT_{c} = E_{0} , whererho = rho_{0} exp (DeltaE/E_{0} ). The emission spectrum shifts with changing excitation (band filling) at lower temperatures (T < T_{c} ) and stays at a constant value independent of excitation at higher temperatures (T > T_{c} ). Experimental results of photoluminescence studies with GaAs crystals show that the quantity E0 , obtained from the dependence of the peak energy upon the degree of excitation is the same as the quantitykT'_{c} , obtained from the dependence of the peak energy upon temperature. This is in agreements with the analysis. For lasing diodes, the threshold will increase steeply with increasing temperature above Tc , if the excited carriers are located mostly in the exponential states of the band tail.E_{0} = (10 sim 20) meV and Tc = (120 sim 250deg K) are typical for crystals of heavily compensated GaAs. 相似文献
14.
《Electron Devices, IEEE Transactions on》1966,13(11):776-777
A thermal feedback model is presented for the analytical definition of the ASO (Area of Safe Operation) for transistors in switching operations. This area is narrowed by the "second breakdown in p-n junction," and the approximate representation of the breakdown threshold is presented. This model consists of a forward and feedback energy flow with gains A and B, respectively.A = V_{CE} times M, B = K times theta times alpha_{R} times I_{e} . Therefore, the condition of the breakdown can be introduced as1 - AB = 0 , whereM is the current multiplication factor, θ is transient thermal resistance,K is a newly introduced current concentration factor, and αR is the temperature coefficient of Ie . Experimental results are also reported for a germanium alloy type transistor. 相似文献
15.
The refractive indices of the ternaryA^{I}B^{III}C_{2}^{VI} semiconductors AgGaS2 , CuGaS2 , and CuInS2 have been measured over the entire range of transparency of these crystals. The optical nonlinear coefficients for second-harmonic generation have also been determined. Three-frequency collinear phase matching is analyzed in detail for AgGaS2 . The birefringences of CuGaS2 and CuInS2 are not large enough to permit three-frequency phase matching within the transparent regions. A parametric oscillator threshold calculation for a pump wavelength 0.89 μ, which is within the range of the GaAs injection laser, indicates that AgGaS2 is promising for this application. The upconversion efficiency in AgGaS2 for sum mixing of the CO2 laser (lambda = 10.5 mu ) with the xenon ion laser (lambda = 0.597 mu ) is also calculated. The result indicates that, depending upon system requirements and the availability of high optical quality material, AgGaS2 can be comparable to ZnGeP2 for upconversion. In Appendix II, we present a theory of the wedge technique for the measurement of nonlinear coefficients. This theory takes into account losses and assumes a Gaussian beam geometry. Furthermore, a discussion of units in nonlinear optics is given. 相似文献
16.
《Electron Devices, IEEE Transactions on》1972,19(1):9-13
It has been found that a harmonic analysis of the usual power-law transfer characteristic of the JFET does not yield equations which accurately predict the third-harmonic distortion products for short-gate structures. However, if field-dependent mobility in the drain-source channel is taken into consideration in the equations for the drain current, a transfer characteristic is obtained of the form3Z_{D}(1-e^{-r})/ Gamma^{2} , where ZD is the normalized channel height and Γ is the field factor. Equations for the distortion products M2 and M3 , which are derived from this type of characteristic, accurately predict M2 and M3 for actual devices as a function of physical parameters. Lower limits on the values of M2 and M3 which can be achieved in a practical JFET are presented. 相似文献
17.
《Electron Devices, IEEE Transactions on》1971,18(12):1186-1187
The noise temperature as a function of the applied field has been measured on an epitaxial silicon layer at the frequencies 2 GHz and 4 GHz. It has been found that the experimental results are in good agreement with the theory given by Moll. It is shown that for noise calculations in silicon field-effect transistors with pronounced carrier velocity saturation the noise temperature Tn versus field E may be approximated byT_{n}/T_{0} = 1 + γ(E/E_{c})^{2} with T0 = lattice temperature, Ec = saturation field, γ = const. 相似文献
18.
We have studied multiple-photon transition in a low-field nuclear magnetic resonance (NMR) experiment. It is well known that a saturation of the NMR occurs when using a sufficiently high alternating magnetic field which induces multiple-photons transitions. We show theoretically that these multiphoton transitions are accompanied by an harmonic generation. For an -photon transition, this generation occurs mostly on then th and (n pm 1 )th harmonic. For an irradiating field2H_{1} cos omega t of pulsation ω such thatnomega= gamma H_{0}=omega_{0} where H0 is the steady field and θ is the angle between H0 and H1 the amplitudesSmin{n}max{n} andSmin{n}max{n+1} of these components are given bySmin{n}max{n} = f_{n}(theta) (H_{1})^{n} ,Smin{n}max{n+1} = cos theta f_{n}(theta) (H_{1})^{n+1} . We have verified these equations in a low-field NMR experiment (H_{0} = 0.7 Gs/s), polarizing first a flowing liquid in a high magnetic field. The liquid then flows in a modified Bloch spectrometer. The receiving coil is still perpendicular to the steady field but it is possible to adjust the angle θ between the axis of the emission coils (H1 field) and the steady-field H0 . Using a synchronous detection at the output of the receiving coil on the pulsation(n - 1) omega, nomega , or(n + 1) omega , we have directly detected multiphoton transistions. The above equations have been verified forn = 2 ton = 5 . There are slight discrepancies at high excitation which may be explained taking into account a large saturation. 相似文献
19.
The CS2 /O2 /N2 O flame laser has been operated for the first time under conditions in which the spectral output is nearly single line. This transition is theP_{10-9} (17) of CO at 5.4265 μm, the same transition which was observed to oscillate in single-line fashion by Hirose et al. in an electrically initiated CO chemical laser. It is suggested that the unique behavior of this line may be due to its close proximity to aP branch transition in an adjacent band, namely theP_{9-8} (23) line, such that the gain profiles of the two lines overlap. Calculations suggest that at the conditions of these experiments, the separation of the line centers for this pair is about 0.3 Å or less. TheP_{10-9} (17) transition was also found to be totally absent under certain conditions of high multiline power, particulary at low O2 and N2 O flows. This may be due to absorption by a high-bandR branch transition at 5.4266 μm, namely theR_{15-16} (32) line. 相似文献
20.
Spectral and temporal measurements of infrared fluorescence (IRF) in SF6 , CF4 , and mixtures of SF6 and CF4 gases excited by a pulsed CO2 laser are reported. Using the 944.2 cm-1[P(20) ] laser line for excitation and measuring the IRF spectra between 700 and 1500 cm-1, a strong red shifted IRF peak of the ν3 mode in pure SF6 was found. No IRF was observed under these conditions in pure CF4 . In a 13:10 mixture of SF6 and CF4 , two strong IRF peaks of the ν3 modes, shifted to the red relative to the room-temperature fundamentals at 948 cm-1and 1283.2 cm-1, were observed. The peaks are almost equal in height and since both molecules have almost the same ν3 band intensity, the present result suggests that efficient intermolecularV-V energy transfer occurs from excited SF6 to cold CF4 molecules. The temporal behavior of the IRF signals under high excitation (langlenrangle approx 6 ) in pure SF6 exhibits two relaxation times, one of bulk cooling withtau_{1} approx 1 ms and the other of aV-T nature withPtau_{2} approx 20 mu s . torr. In the mixture, an additional relaxation of the intermolecularV-V energy transfer process is observed withPtau_{3} approx 10 mu s . torr. The red shift dependence of the IRF peaks on the degree of excitation was also measured and used to examine population distributions, specific IRF transitions, and anharmonicity parameters. 相似文献