The M54564P and M54564FP each have eight circuits, which are made of input inverters and current-sourcing outputs. The outputs are made of PNP transistors and NPN Darlington transistors. The PNP transistor base current is constant. Resistance of 50k is connected between each output pin and GND, making these ICs suitable for fluorescent display tubes. VS and GND are used commonly among the eight circuits.