QuestionApril 20, 2025

If the inputs of a 74139 dual four-line demultiplexer are as shown below, which output is correct? bar (E)_(a)=databar (E)_(b)=data AO_(a)=1AO_(b)=0 A1_(a)=0A1_(b)=0 O_(a)=data 1_(b)=data 2_(a)=data 2_(b)=data 1_(a)=data 1_(b)=data 1_(a)=data O_(b)=data

If the inputs of a 74139 dual four-line demultiplexer are as shown below, which output is correct? bar (E)_(a)=databar (E)_(b)=data AO_(a)=1AO_(b)=0 A1_(a)=0A1_(b)=0 O_(a)=data 1_(b)=data 2_(a)=data 2_(b)=data 1_(a)=data 1_(b)=data 1_(a)=data O_(b)=data
If the inputs of a 74139 dual four-line demultiplexer are as shown below, which output is correct? bar (E)_(a)=databar (E)_(b)=data AO_(a)=1AO_(b)=0 A1_(a)=0A1_(b)=0 O_(a)=data 1_(b)=data 2_(a)=data 2_(b)=data 1_(a)=data 1_(b)=data 1_(a)=data O_(b)=data

Solution
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Answer

The correct output is O_a = 1 and O_b = 0. Explanation 1. Identify the Enable Inputs The enable inputs \bar{E}_a and \bar{E}_b are both set to 'data', which means they are active low. If they are not low, the outputs will be disabled. 2. Determine Active Outputs For a demultiplexer, when enabled, one of the outputs is selected based on the address lines. Here, AO_a = 1 and AO_b = 0. 3. Analyze Address Lines The address lines A1_a = 0 and A1_b = 0 indicate that the first output line is selected for both sections. 4. Evaluate Output Conditions Since AO_a = 1, it indicates that the output corresponding to the address lines should be high. For AO_b = 0, the output should be low.

Explanation

1. Identify the Enable Inputs<br /> The enable inputs $\bar{E}_a$ and $\bar{E}_b$ are both set to 'data', which means they are active low. If they are not low, the outputs will be disabled.<br /><br />2. Determine Active Outputs<br /> For a demultiplexer, when enabled, one of the outputs is selected based on the address lines. Here, $AO_a = 1$ and $AO_b = 0$. <br /><br />3. Analyze Address Lines<br /> The address lines $A1_a = 0$ and $A1_b = 0$ indicate that the first output line is selected for both sections.<br /><br />4. Evaluate Output Conditions<br /> Since $AO_a = 1$, it indicates that the output corresponding to the address lines should be high. For $AO_b = 0$, the output should be low.
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