Vol. 22, No. 8 (1966)
In the design of an emitter of power transistors, the main problem is to attain good current amplification factor β for a given injection level. At a higher injection level, the current amplification factor drops off as the emitter current density is increased. One of the commonly used methods to reduce this fall-off is by increasing the emitter area. On account of the socalled "base region self-crowding effect", this would make the emitter current density not uniform over the emitter junction area, the current density dropping off rapidly at regions far from the base contact. In this paper, this effect is analyzed quantitatively for nearly all injection levels both for circular and comb structures of the junction. An "exponential decay" for the emitter current density distribution, and an effective emitter area are obtained. These results may give some reference for the design of power transistors.
1966, 133 (8): 911-918. doi: 10.7498/aps.22.911
In this paper, a method of measuring the piezoelectric properties of ADP crystal by introducing a dynamic capacitance as well as increasing the capacitance CT in series with the vibrator and correcting the static capacitance C0 is described. The results of measurement are satisfactory.
1966, 133 (8): 919-929. doi: 10.7498/aps.22.919
A general principle of the direct analogue simulation of static field components was searched for. As an application of this method, the simulation of the field of a semi-infinite solid solenoid was investigated. The results obtained show that, for several special static systems, it is able to accomplish direct simulations and it has considerable advantages. The simulating solution of the above cited solenoid was given by Bz and ψ curves. With these graphs, the solution of the distribution of field strengths and force lines of any solenoid can be facilitated.
1966, 133 (8): 930-944. doi: 10.7498/aps.22.930
An analysis is made for the initial current, the operation current limit, and the critical threshold current of the injection laser at continuous and pulse operation conditions. Both the heat generated at junction and bulk heat generation have been taken into account simultaneously, the later can be characterized with a normalized equivalent bulk heating resistance r. For the continuous operation case, it is shown that the bulk heat generation cannot often be neglected. In the analysis for pulse operation case, the effect of pulse duration and that of repetition frequency have been considered respectively. It is indicated that when both the high power and high repetition frequency operation are desirable, it will be optimum to choose the duty cycle approach to 0.03. In some applications where the repetition frequency is not an important factor, to make the repetition period just three times larger than the thermal relaxation time of lasers is suitable. As the repetition frequency increased sufficiently, the performance of lasers is determined by the duty cycle mainly. Examples of the analysis applied to some typical cases have been illustrated and the emission spectral band broadening originated from junction temperature variation during pulse operation is briefly discussed.
1966, 133 (8): 945-951. doi: 10.7498/aps.22.945
Using the intermediate vector boson (IVB) theory and Cabibbo's SU3 model for the weak interaction, the analytical expressions and numerical results for the differential cross-sections and the longitudinal polarizations of the final state particles of several νN "elastic" reactions have been obtained. The results show that, for the given set of form factors usually assumed, the IVB effects on the longitudinal polarizations of the leptons and the hyperons are substantial near certain outgoing angles when the neutrino energy is high enough. The results also show that some informations about the form factors and the mass of the IVB can be obtained from the experimental results of the differential cross-section and the longitudinal polarization taken together if they are accurate enough. The nuclear effects and the effect of the neutrino beam energy spectrum on the longitudinal polarization of the muon have also been estimated for the process νμ + [ Z, A ] →μ- + [Z + 1, A].