在DA转换器中通常用哪两项来描述转换精度，分别描述这两个性能指_爱下问搜题

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问题问答题简答题

在DA转换器中通常用哪两项来描述转换精度，分别描述这两个性能指标？

答案

参考答案：在D/A转换器中通常用分辨率和转换误差来描述转换精度。

分辨率是指输入数字量最低有效位为1时，对应输出可分辩的电压变化量△V与最大输出电压Vm之比

转换器中各元件参数的偏差，基准电压的波动，和运放的零点漂移都可以影响D/A的转换精度。

完形填空

When you think of American culture, what first comes to your mind? McDonald’s? Coca Cola? Levi’s? Disneyland? Michael Jordan? Julia Roberts? Many people   小题1:  American culture is a   小题2: of popular symbols like these. Actually, these symbols are only one    小题3:  part of American culture—pop culture.
What is pop culture? Well, pop is   小题4:   for popular. The origins of pop culture can often be traced to popular movies, television shows, music stars and sports figures. Pop culture is   小题5:  promoted by business and advertising. The most   小题6:  examples of American pop culture appear among high school and college students. Trends (趋势)   小题7:  by famous personalities quickly become part of young people’s    小题8: .
American pop culture has spread around the world. One major reason for its  小题9:  is that English is a universal language. English is the language of diplomacy, international business and transportation.   小题10:  language and culture go together, learning English means becoming   小题11:  of English-speaking cultures. Besides, America is a world   小题12:  in movies, music and magazines. The kind of American culture   小题13:  in those media is pop culture. Finally, pop culture is easy to package and to   小题14: . For that reason, it is easy to “sell” to the world.
Many people believe that American pop culture is what American is all   小题15:  . Does pop culture   小题16:   the true culture of America? Yes and no. Pop culture does 小题17:  a portion (比例) of American society — especially the   小题18:  young people that are tuned in to the media. But American pop culture is faddish (流行一时的) and    小题19:   . If you want to learn about real American culture, you’ll have to go a little    小题20:    than McDonald’s.

B．communicated

C．ever-changing

D．ever-lasting

问答题简答题

分析发动机功率不足的原因。