Subthreshold current reduction for decoded-driver by self-reverse biasing [DRAMs]

Analytical expressions are presented for subthreshold current reduction in a decoded-driver by self-reverse biasing, which is inherently required for low-voltage, low-power, high-speed DRAM´s for portable equipment. The scheme involves inserting a switching MOS transistor between the driver circuits and its power supply line. The subthreshold current of the decoded-driver is reduced to the order of 10 ^-3 in the practical temperature range (250-350 K) with 254 mV of self-reverse biasing voltage, while the delay time is only 3% more than in conventional schemes. The transition time of 1 ms from the operating state to the low subthreshold current state is sufficient to reduce the subthreshold current. The rapid recovery time of 1 ns from the low subthreshold current state does not interrupt the start of normal operation. The subthreshold current reduction was confirmed experimentally using a test chip fabricated with 0.25-μm technology