A driving element and a wiring section electrically connected to the driving element are formed on a base substrate. A first ground pattern outputting a reference voltage of the driving element is formed on the base substrate. The base substrate includes a second ground pattern which is spaced apart from the first ground pattern. An external connection section is included on the base substrate, the external connection section being connected to the first and second ground patterns. A connecting cable contacts the external connection section to permit the first and second ground patterns to be connected to external circuitry.