应该是be done才可表被动吧?那什么时候单独done表被动???

总结了几点，不一定全面，欢迎补充：
1.done在定语中表示被动，如：
He told us of the great wrong done to him.=He told us of the great wrong which had been done to him.他给我们讲了他所遭受的巨大冤屈。
a report done by the government=a report which was done by the government 一个由政府制作的报告

2.done在with复合结构中表示被动，如：
With the homework done, I went out for a walk.=When the homework was/had been finished, I went out for a walk.作业做完之后,我出去散了会儿步。

3.连词后的done表被动,引导状语从句的连词(如when, while, though, once, as if等),单独采用done表示被动,相当于一个省略的状语从句。如：
The Chinese do not typically use exaggerated gestures or facial expressions while speaking, and may find them distracting when done by others 中国人在讲话过程中不做夸张的动作或者面部表情，而且不欣赏别人做出类似动作。when done by others= when they are done by others