Typically, driver circuits are utilized with an operational amplifier which provides an output signal varying between a positive supply voltage V.sub.DD and a negative supply voltage V.sub.SS relative to an intermediate analog ground voltage potential V.sub.AG. In an attempt to reduce power dissipation, CMOS operational amplifiers may be designed for Class B operation where two output devices are nonconductive simultaneously when the output signal is near analog ground. However, severe cross-over distortion exists in class B operation when the output crosses the V.sub.AG potential in either direction. Therefore, Class AB operation is frequently more desirable. In Class AB operation, two output devices are simultaneously conductive when the output signal is near analog ground. Class AB operation minimizes cross-over distortion which is characteristic of Class B operation. However, circuits which reduce cross-over distortion may minimize the distortion at the expense of excessive quiescent DC current resulting from the simultaneous operation of the output devices at positive or negative voltages anywhere close to V.sub.AG. Therefore, both output devices must be restricted to be jointly conductive only when the output signal is within a minimum threshold voltage of V.sub.AG. Such a circuit is described in U.S. Pat. No. 4,336,503 which is assigned to the same assignee as the instant application. However, such a circuit must be carefully designed to prevent oscillation as noted therein. Other known circuits which attempt to minimize cross-over distortion either have excessive quiescent output current or introduce undesirable design limitations.
USPTO Backgrounds
USPTO Backgrounds