Features
1) The built-in bias resistor allows the configuration of an inverter circuit without connecting any external input resistors (see Equivalent circuit).
2) Each bias resistor is a thin-film resistor. Since they are completely insulated, the input can be positively biased. The insulation also eliminates most of the parastic effects.
3) Circuit design is simplified since only the OFF and the ON conditions have to be set.

Structure
  PNP digital transistor (with built in resistors).