Abstract-This paper discusses the design, fabrication, and test of a CMOS active clamp circuit. The active clamp is a linear voltage regulator, with a voltage deadband to allow for voltage ripple, that is designed to operate in parallel with a switchmode voltage regulator. Its specific function is to sink or source large transient currents to microprocessor loads, thus allowing operation with very small output capacitance. Laboratory tests on a prototype IC exhibit stable behavior with negligible overshoot with only 47 microfarads of output capacitance with loads of about nine amperes. Output impedances of 2-3 m are achieved.

Present day microprocessors such as the Intel Pentium Pro require over loamps of supply current at voltages in the range of 2-3.3volts. The load demand can exhibit abrupt changes from light load (<0.5amps) to full load in a matter of few hundred nanoseconds. Future processor generations are projected to require greater current (up to 60amps) at supply voltages as low as lvolt. Furthermore, these future processors are projected to impose load steps with on the order of 5amp/nS when the processor switches between inactive and active modes, or viceversa. In this paper, we discuss some of the ramifications for the design of the power supply required to supply these microprocessor loads. We focus on the use of a paralleled active circuit which can be thought of as an active clamp which is designed to support the load during transients. Breadboards of these circuits have been built and tested. A prototype IC design is currently under test.

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In 1898, the year before his death, the German missionary Ernst Faber reflected on his forty-year career in China. The account of his early missions work was suffused with a tone of failure and disappointment. He wrote openly about his difficulties in adjusting to the climate and environment of southern China, the diminutive numbers of converts to Christianity, his frustrations with learning Mandarin and the local dialects used in Guangdong, and the overwhelming feeling of loneliness that he encountered working in rural parishes.