第14题: [单项选择]When the coach realized the team was under great______before the competition, he told a few jokes to relax them. A. crisis B. stress C. nervousness D. excitement 参考答案:B 答案解析:这道题考查名词的近义辨析和固定搭配。stress的固定词组“be under stress/ suffer from stress” “在压力下/受到压力”;crisis“危机,决定性时刻”;nerv
第19题: [单项选择]已知三极管工作在放大区RC=1.5kΩ,RS=2kΩ,其小信号模型(微变等效电路)参数rbe=1kΩ,若所有的电容都足够大,则该电路的输出电阻ro最接近于( )kΩ。 A. 0.5 B. 1 C. 1.5 D. 2 参考答案:C 答案解析:[解析] 输出电阻为放大电路去掉电源(输入端短路)后,断开负载电阻,从输出端看入的等效电阻,根据该电路的微变等效电路得知,ro=RC=1.5kΩ。