SEMICONDUCTOR INTEGRATED CIRCUIT HAVING VARACTOR DEVICE

摘要

PURPOSE: A semiconductor integrated circuit having varactor device is provided to switch a transistor at a high speed by providing a circuit for pumping charges up or down compulsorily in the quantity required for turning the transistor ON or OFF. CONSTITUTION: A CMOS line driver(10) is made up of p- and nMOS transistors(11,12). A pMOS varactor is interposed between the source of the pMOS transistor(11) and a power supply, while an nMOS varactor is interposed between the source of the nMOS transistor(12) and ground. The sizes of each of these MOS varactors may be the same as those of the p- or nMOS transistor(11,12). Alternatively, each of these MOS varactors may have a channel area twice greater than that of the p- or nMOS transistor(11,12). The inverted version of a signal input to the line driver is supplied to the gates of the MOS varactors. In this manner, the MOS transistors(11,12), making up the line driver, can switch at a high speed.