Encoders, Decoders, and Multiplexers Quiz Quiz

Explore essential digital logic concepts with this quiz on encoders, decoders, and multiplexers. Assess your understanding of circuit functions, applications, and signal operations in digital electronics while sharpening your knowledge of these key components.

1. Encoder Output Lines

   If a digital encoder has 8 input lines, how many output lines does it typically have?

   1. 8
   2. 2
   3. 3
   4. 4

   Explanation: For an encoder, the number of output lines needed to represent n input lines is determined by the formula: number of output lines = log2(number of input lines). For 8 inputs, log2(8) equals 3, so the correct answer is 3. Option 2 is too few to represent all 8 input lines uniquely. Option 4 might seem reasonable, but it is more than necessary for 8 inputs. Option 8 simply repeats the number of inputs, which is not how encoders function.

2. Multiplexer Data Selection

   In a 4-to-1 multiplexer, what determines which input is connected to the output at a given moment?

   1. Select lines
   2. Data clock
   3. Output signal
   4. Enable signal

   Explanation: Select lines are used to choose which one of the multiple inputs gets passed to the output in a multiplexer. The enable signal can activate or deactivate the device but does not select an input. The output signal is the result, not a control mechanism. A data clock might control timing, but not input selection in standard multiplexing.

3. Decoder Functionality Example

   A 2-to-4 line decoder receives an input of '10'. Which output line will be active, assuming active-high outputs?

   1. O0
   2. O3
   3. O1
   4. O2

   Explanation: A decoder takes a binary value and activates the corresponding output; '10' in binary represents the decimal number 2, so line O2 will be active. O0 and O1 correspond to binary values '00' and '01' respectively, and O3 corresponds to '11'. Only O2 correctly reflects the given input.

4. Applications of Encoders

   Which situation best demonstrates the use of an encoder in a digital system?

   1. Selecting one of many data lines
   2. Converting input requests into binary code
   3. Amplifying signal strength
   4. Transforming parallel data to serial data

   Explanation: Encoders convert multiple input signals into a smaller number of outputs, usually binary code, as seen in devices like keypad encoders. Transforming parallel to serial data is a function of a serializer, not an encoder. Selecting data lines is the role of a multiplexer, while amplifying signals is a function of analog amplifiers, not encoders.

5. Multiplexer Control Signals

   How many control or select lines are needed for a 16-to-1 multiplexer to operate properly?

   1. 2
   2. 16
   3. 8
   4. 4

   Explanation: A multiplexer needs a number of select lines equal to log2 of the number of inputs. For 16 inputs, log2(16) equals 4, so 4 select lines are required. Option 2 is insufficient, 8 is excessive and unnecessary, and 16 would match the input lines, which is not the way select lines are determined.