Power integrated circuits (ICs) or power ICs may be used to supply power in variety of different applications.  For example, power ICs may be used to supply power in pulse width modulation circuits.  A drive IC may be used to provide input voltages and control signals to the power IC.  Therefore, the drive IC and the power IC must be connected together.  However, the drive IC and the power IC may be implemented using different IC technology.  For example, the power IC may be implemented using MOSFET technology and the drive IC may employ standard IC technology.  Therefore, packaging of the power IC and the drive IC may be problematic. 
Typically, an integrated circuit (IC) is designed with pads, which are used to provide external connections to the IC.  The IC is typically mounted on a package, which may include pins for connecting the package and its circuits to other electronic devices.  The pins of the package are sometimes connected to the pads of the IC using bondwires.  The bondwires, however, may have a resistance that is greater than 50-100 mΩ. The combined resistance of the bondwires increases the power dissipation of the IC.  Therefore, when the IC has a large number pads that need connections, bondwires may not be an acceptable approach.  To reduce parasitic packaging resistance, wires and/or traces that are arranged on a substrate such as a printed circuit board are sometimes used to provide interconnects.  While this approach offers some improvement over bondwires, the wires and/or traces also have unacceptably high parasitic packaging resistance for ICs requiring a large number of connections. 
ICs may include a large number of interconnected transistors.  The transistors and other circuit elements are interconnected in various ways to provide desired circuit functions.  It is usually most efficient to fabricate multiple ICs on a single wafer.  After processing, the ICs that are fabricated on the wafer are separated and then packaged.  The wafer can accommodate a fixed number of ICs for a given IC size.  Reducing the size of individual transistors in the IC may help to reduce the overall size of the IC.  This, in turn, allows an increased number of ICs to be made on each wafer and reduces the cost of the ICs.