问题 问答题 简答题

什么是A/D转换器?举例说明其特点?

答案

参考答案:

随着数字电子技术的迅速发展,用数字电路处理模拟信号的情况越来越多。为了能够用数字系统处理模拟信号,必须把模拟信号转换成相应的数字信号,这种转换称为模数转换(或称为A/D转换),完成这种转换功能的器件称为A/D转换器。

例如:7126A/D转换器就是其中的一种。

该电路具有以下特点:

①单电源供电,电压范围在7—15V之间,功耗约1MW。

②采用CMOS差分输入,输入阻抗高,大于10Ω。

③驱动电路简单,可直接驱动液晶显示器。

④自动辨别信号极性。

⑤利用内部模拟开关实现自动零点调整与极性转换,嗓声低,温漂小。

阅读理解

根据短文,判断正(T)误(F)。

  While at the park one day, a woman sat down next to a man on a bench near

a playground. "That's my son over there," she said, pointing to (指着) a little boy

in a red sweater.

  "He's a fine looking boy," the man said. "That's my daughter on the bike in

the white dress." Then, looking at his watch, he called to his daughter: "We have

to leave for home now, Melissa."

  "Just five more minutes, Dad," Melissa said. "Please? Just five more

minutes."

  The man nodded (点头) and Melissa went on riding her bike happily.

Minutes passed and the father stood and called again to his daughter, "Time to go

now?"

  "Five more minutes, Dad," Melissa said again. "Just five more minutes."

  The man smiled and said: "OK."

  "Oh, you really are a patient father," said the woman.

  The man smiled and then said: "Her older brother Tommy died (死) in a

traffic accident last year while he was riding his bike near here," the man said. "I

never spent much time with Tommy and now I'd give anything for just five more

minutes with him. I've vowed (发誓) not to make the same mistake with Melissa.

She thinks she has five more minutes to ride her bike. The truth is, I get five more

minutes to watch her play."?

( ) 1. The man's daughter and her brother were playing at the park.

(     ) 2. The man felt sorry that he didn't give more of his time to his older son.

(     ) 3. Melissa wanted to stay longer when her father asked her to go the first time.

(     ) 4. Melissa agreed to go home when her father called her the second time.

( ) 5. The man learned a lot from Tommy's death.

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