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Table Of Contents
Modern Computer Architecture and Organization - Third Edition
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A single bit in a standard dynamic random-access memory (DRAM) integrated circuit is composed of two circuit elements: a MOSFET and a capacitor. We begin with a description of the capacitor and its function in computer memory.
A capacitor is a two-terminal passive circuit element that stores energy. Energy enters and leaves a capacitor as electrical current. The voltage across the capacitor terminals is proportional to the amount of electrical energy contained in the capacitor.
To continue the hydraulic system analogy introduced in Chapter 2, Digital Logic, think of a capacitor as a balloon attached to the side of the pipe leading to a water tap. Water pressure in the pipe causes the balloon to inflate, filling it with some of the water from the pipe. Let's assume this is a sturdy balloon and that, as it inflates, it stretches, increasing the pressure within. The balloon continues to fill until its internal pressure equals the...