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【多选题】
下列关于高频谐振小信号放大器自激的原因,描述正确的是
A.
晶体管为双向器件,内部存在反向传输导纳,所以当放大器的正反馈能力抵消了回路损耗能量,且电纳部分也恰好抵消时,放大器失去放大性能,处于自激振荡工作状态
B.
晶体管为双向器件,内部 集电结电容不能忽略 ,所以当放大器的正反馈能力抵消了回路损耗能量,且电纳部分也恰好抵消时,放大器失去放大性能,处于自激振荡工作状态
C.
晶体管为双向器件,内部存在正向传输导纳,所以当放大器的正反馈能力抵消了回路损耗能量,且电纳部分也恰好抵消时,放大器失去放大性能,处于自激振荡工作状态
D.
晶体管为双向器件,内部存在反向传输导纳,所以当放大器的负反馈能力抵消了回路损耗能量,且电纳部分也恰好抵消时,放大器失去放大性能,处于自激振荡工作状态
E.
晶体管为双向器件,内部 集电结电容不能忽略 ,所以当放大器的负反馈能力抵消了回路损耗能量,且电纳部分也恰好抵消时,放大器失去放大性能,处于自激振荡工作状态
F.
晶体管为双向器件,内部存在正向传输导纳,所以当放大器的负反馈能力抵消了回路损耗能量,且电纳部分也恰好抵消时,放大器失去放大性能,处于自激振荡工作状态
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【单选题】称取葡萄糖10.00g,加水溶解并稀释至100.0ml,于20℃用2dm测定管,测得溶液的旋光度为+10.6°,此葡萄糖的比旋度为
A.
53.0°
B.
-53.0°
C.
0.53°
D.
+106°
E.
+53.0°
【单选题】Some Heads of Government now fear that negotiations will ______ before a settlement is reached.
A.
wear out
B.
come along
C.
break off
D.
end up
【单选题】—Whose dictionary is this? —It must belong _________. [     ]
A.
Carol
B.
Carol's
C.
to Carol
D.
to Carol's
【单选题】The Changbaishan Mountains have a huge variety of scenery, some of the best of _____ can only be reached on foot. [     ]
A.
that
B.
which
C.
what
D.
where
【单选题】What does Carol offer to do?
A.
Make travel arrangements
B.
Meet with some visitors
C.
Order food for a meeting
D.
Remind employees of a policy
【单选题】Carol _____ some reading and _______ English yesterday.
A.
did, practiced
B.
did, practicing
C.
do, practiced
D.
does, practices
【单选题】称取葡萄糖10.00g,加水溶解并稀释至100.0ml,于20℃用2测定管,测得溶液的旋光度为+10.6°,此葡萄糖的比旋度为()
A.
53.0°
B.
-53.0°
C.
0.53°
D.
+106°
E.
+53.0°
【单选题】- What am I going to do about a present for Carol? - You______some flowers.
A.
might have sent her
B.
must have sent her
C.
could send her
D.
would send her
【简答题】Jesse McCartney began entertaining and delighting audiences at a very early age in off-Broadway stage shows including Oliver, A Christmas Carol, and Annie Get Your Gun. At the age of seven, he began a...
【单选题】称取葡萄糖100.0g,加水溶解并稀释至100.0ml,于20°C用2dm测定管,测得溶液的旋光度为+10.5°,求其比旋度为
A.
+52.5°
B.
-26.2°
C.
+5.25°
D.
-52.7°
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