直流斩波电路（DC Chopper）的功能是将一个变化的直流电压变成另一种固定的或可调的直流电压。

A、逆变(Inversion)

B、整流(Rectification)

C、斩波(DC Chopping)

D、交流调压(AC Voltage Conversion)

E、变频(Frequency Conversion)

Adrienne Popper

在图所示电路中，运算放大器的最大输出电压U_OPP=±12V，稳压二极管的稳定电压U_Z=6V，其正向压降U_D=0.7V，u_i=12sinωtV。在参考电压U_R=+3V和-3V两种情况下，试画出传输特性和输出电压u_o的波形。

   

-6)V,开环电压增益为70dB.图P9.14所示LM1877N-9中一个通道组成的实用电路,电源电压为24V,C₁~C₃对交流信号可视为短路;R₃和C₄起相位补偿作用,可以认为负载为8Ω.

(1)图示电路为那种功率放大电路?

(2)静态时u_p、u_N、u_o、u_o各为多少?

(3)设输入电压足够大,电路的的最大输出功率P_om和效率?各为多少?

Oppenauer 氧化中的氧化剂是()

A.异丙醇铝

B.叔丁醇铝

C.环己酮

D.丙醛

According to the conversation, an ethical shopper should

A. consider the worth of something to be bought.

B. ask for others' advice before buying things.

C. postpone buying things whenever possible.

D. search for things that are less costly.

Oppenauer 氧化中的催化剂是()

A.异丙醇铝

B.氢氧化铝

C.环己酮

D.丙酮

A supermarket usually has（ ）

A．lots of rooms for shoppers to sit in

B．lots of rest rooms for shoppers to use

C．ample space for shoppers to move round

D．lots of rooms where new varieties of goods are on display