Operational Trans conductance Amplifiers:Truth Tables

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Truth Tables

The value of a function f for different combinations of values of variables can be shown in a table, as exemplified in Tables 26.1 and 26.2. The table for n variables has 2n rows. Thus the table size increases rapidly as n increases.

Under certain circumstances, some of the combinations of input variable values never occur, or even if they occur, we do not care what values f assumes. These combinations are called don’t-care conditions, or simply don’t-cares, and are denoted by “d” or “*”, as shown in Table 26.2.

Expressions of Logic Functions-0335

Decimal Specifications

A concise means of expressing the truth table is to list only rows with f = 1 and d, identifying these rows with their decimal numbers in the following decimal specifications. For example, the truth table of Table 26.2 can be expressed, using Σ , as

Expressions of Logic Functions-0336

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