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Power

Every digital IC consumes power, and this is an important parameter in digital system design, especially in portable products.

Consider, e.g., a TTL IC with all gate outputs in the H state. The gate will draw a current I_CCH from the power supply voltage rail, at voltage V_CC. In the L state, the current drawn is I_CCL. The average current drawn is

$$I_{CC(ave)} = \frac{I_{CCH} + I_{CCL}}{2}$$

Therefore the average power consumed by the IC is

$$P_{D(ave)} = I_{CC(ave)} \times V_{CC}$$