常用的晶体管整流电路有哪几种？
参考答案：
常用的晶体管整流电路有半波整流电路、全波整流电路、桥式整流电路、倍压整流电路和特殊整流电流。
—How long have you been working as an assistant here?
—__________I finished middle school.
A．Ever since
B．Before
C．After
D．When
双锥回转真空干燥机真空度是多少？
