# Digital Circuits Questions and Answers – Encoders

This set of Digital Electronics/Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Encoders”.

1. How many inputs will a decimal-to-BCD encoder have?
a) 4
b) 8
c) 10
d) 16

Explanation: An encoder is a combinational circuit encoding the information of 2n input lines to n output lines, thus producing the binary equivalent of the input. Thus, a Decimal-to-bcd converter has decimal values as inputs which range from 0-9. So, a total of 10 inputs are there in a decimal-to-BCD encoder.

2. How many outputs will a decimal-to-BCD encoder have?
a) 4
b) 8
c) 12
d) 16

Explanation: An encoder is a combinational circuit encoding the information of 2n input lines to n output lines, thus producing the binary equivalent of the input. Thus, a decimal to BCD encoder has 4 outputs.

3. How is an encoder different from a decoder?
a) The output of an encoder is a binary code for 1-of-N input
b) The output of a decoder is a binary code for 1-of-N input
c) The output of an encoder is a binary code for N-of-1 output
d) The output of a decoder is a binary code for N-of-1 output

Explanation: An encoder is a combinational circuit encoding the information of 2n input lines to n output lines, thus producing the binary equivalent of the input. It performs the opposite operation of a decoder which results in 2n outputs from n inputs. Thus, an encoder different from a decoder because of the output of an encoder is a binary code for 1-of-N input.

4. If we record any music in any recorder, such types of process is called ___________
a) Multiplexing
b) Encoding
c) Decoding
d) Demultiplexing

Explanation: If we record any music in any recorder, it means that we are giving data to a recorder. So, such process is called encoding. Getting back the music from the recorded data is known as decoding.

5. Can an encoder be a transducer?
a) Yes
b) No
c) May or may not be
d) Both are not even related slightly

Explanation: Of course, a transducer is a device that has the capability to emit data as well as to accept. Transducer converts signal from one form of energy to another.
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6. How many OR gates are required for a Decimal-to-bcd encoder?
a) 2
b) 10
c) 3
d) 4

Explanation: An encoder is a combinational circuit encoding the information of 2^n input lines to n output lines, thus producing the binary equivalent of the input.
This is clear from the diagram that it requires 4 OR gates:
.

7. How many OR gates are required for an octal-to-binary encoder?
a) 3
b) 2
c) 8
d) 10

Explanation: An encoder is a combinational circuit encoding the information of 2n input lines to n output lines, thus producing the binary equivalent of the input. Thus, in octal to binary encoder there are 8 (=23) inputs, thus 3 output lines.

8. For 8-bit input encoder how many combinations are possible?
a) 8
b) 2^8
c) 4
d) 2^4

Explanation: An encoder is a combinational circuit encoding the information of 2n input lines to n output lines, thus producing the binary equivalent of the input. There are 28 combinations are possible for an 8-bit input encoder but out of which only 8 are used using 3 output lines. It is a disadvantage of encoder.

9. The discrepancy of 0 output due to all inputs being 0 or D0, being 0 is resolved by using additional input known as ___________
a) Enable
b) Disable
c) Strobe
d) Clock

Explanation: Such problems are resolved by using enable input, which behaves as active if it gets 0 as input since it is an active-low pin.

10. Can an encoder be called a multiplexer?
a) No
b) Yes
c) Sometimes
d) Never

Explanation: A multiplexer or MUX is a combination circuit that contains more than one input line, one output line and more than one selection line. Whereas, an encoder is also considered a type of multiplexer but without a single output line and without any selection lines.

11. If two inputs are active on a priority encoder, which will be coded on the output?
a) The higher value
b) The lower value
c) Neither of the inputs
d) Both of the inputs

Explanation: An encoder is a combinational circuit encoding the information of 2n input lines to n output lines, thus producing the binary equivalent of the input. If two inputs are active on a priority encoder, the input of higher value will be coded in the output.

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