发光二极管是一种将电能转变成光能的半导体器件，是由（    ）组成。

<span style、"font-family: 'Times New Roman',serif; font-size: 10.5pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt;" lang="EN-US">2个PN结</span>

<span style、"font-family: 'Times New Roman',serif; font-size: 10.5pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt;" lang="EN-US">3个PN结</span>

<span style、"font-family: 'Times New Roman',serif; font-size: 10.5pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt;" lang="EN-US">4个PN结</span>

、1个PN结