A CMOS logic element wherein the dynamic pull-up current is supplied by an unregulated power rail

摘要

The output stage of a clocked CMOS logic element comprises pull-up transistors 30 and 38 connected to regulated and unregulated supply rails 34 and 40 at 1.5 volts and 3.6 volts respectively. Device 38 is enabled to provide pull-up current during a positive output transition and is then turned off by the control circuit 42 when the output node 28 attains a voltage near the regulated voltage 34. The provision of a large part of the dynamic current requirement directly from the battery improves overall efficiency, which is of benefit in mobile phones. The dynamic power is supplied directly from the battery and so no conversion losses are incurred in reducing the voltage to a lower level. The complexity, size and cost of the power supply is reduced because the regulated power supply is no longer required to provide large dynamic currents.