问题一:何为正负过零?
问题二:U2A,U2B,输出端电容和二极管为何那样接?
请大家说说此电路到低是怎么工作的?
![](http://u.dianyuan.com/bbs/u/54/1842911183007157.jpg?x-oss-process=image/watermark,g_center,image_YXJ0aWNsZS9wdWJsaWMvd2F0ZXJtYXJrLnBuZz94LW9zcy1wcm9jZXNzPWltYWdlL3Jlc2l6ZSxQXzQwCg,t_20)
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