In plasma displays in different inch sizes, there is a disadvantage in that because each of the plasma displays in different inch sizes has an output semiconductor device with a different outer shape, a pitch of the external lead and the number of the output semiconductor devices vary, so that printed circuit boards need be designed differently for the different inch sizes. A hybrid integrated circuit includes mounting portions which are composed of a conductive path on an insulated metal substrate, and into which at least an output semiconductor device of a discharge maintaining circuit is incorporated, and includes external terminals arranged at a constant pitch. When the inch size of the plasma display is changed, the mounting portions are designed to have a size enough to accommodate the output semiconductor device for the greatest inch size. Thus, the same hybrid integrated circuit is commonly used.