The safe working load for the assembled cargo gear and the minimum angle to the horizontal for which the gear is designed shall be marked on the ______.
【简答题】在图P3.9的三极管开关电路中,给定V CC =5V,R C =1kΩ,R B =5.1kΩ,输入信号的高、低电平分别为V IH =2.4V、V IL =0.3V。若三极管的电流放大系数β=40,饱和压降V CE(sat) =0.1V,饱和导通内阻R CE(sat) = 20Ω,若R C 改为510Ω,R B 改为4.7kΩ,试计算β应当取多大才能保证v I 为高电平时三极管工作在饱和导通状态。