I'm new to electronics and I have a problem with driving several (66) 4" high 7 Segment display which requires a 12V supply but are controlled through a Arduino +expander I/O. I have purchased a transistor array but found that it has a common positive V. I need individual grounded emitters. I cannot find a common-ground transistor array on the market so I will probably have to use individual transistors (i.e. 66 x 7 = 462 transistors) . I am struggling to specify the correct transistor to use. Can anybody point me in the right direction.