一般来说，对于输入信号源为电压源的放大电路，其输入电阻 Ri应。
查看答案
输入电阻是从放大电路输入端看进去的等效电阻，即放大器是信号源的一个。
What is Alice's future hope?
A. She wants to be a teacher in China.
B. She wants to travel and see the world.
C. She wants to teach Chinese in the U.K.
D. She wants to study in a teacher training college.
What would Tom like to do when he graduates?
A. He has no plans.
B. He wants to start a blog.
C. He wants to make a movie about his travels.
D. He wants to travel through Asia and Europe.
How do young people in England feel about their futures?
A. They think they will have an easy life.
B. They want to take advantage of their opportunities.
C. They feel they have fewer opportunities than their parents.
D. They are hopeful about the jobs they will have after graduation.
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