The function of ExtRegulator for mc33774a

[JhonYF]

as shown above,why do it need a transistor ？ 

[guoweisun]

Those're their definition you can see below picture:

[JhonYF]

Why do it need this transistor? What difference does it make？

[guoweisun · Accepted solution]

你可以理解为他只是一个LDO/regulator的控制器，里面并没有集成功率器件三极管MOSFET，所以才需要外加，就是没有集成进去功率器件。