Question

For a 4-bit Flash type Analog to Digital Converter (ADC) with full scale input voltage range "V", which of the following statement(s) is/are true?

• A. The ADC requires 15 comparators.
• B. The ADC requires one 4 to 2 priority encoder and 4 comparators.
• C. A change in the input voltage by \( \frac{V}{16} \) will always flip MSB of the output.
• D. A change in the input voltage by \( \frac{V}{16} \) will always flip the LSB of the output.

Hint:

In a Flash ADC, the number of comparators is \( 2^n - 1 \) where \( n \) is the number of bits. For a 4-bit ADC, 15 comparators are needed.

Answer 1

The Correct Option is A, D

For a 4-bit Flash ADC, the number of comparators required is \( 2^n - 1 \), where \( n \) is the number of bits. For a 4-bit ADC, this gives \( 2^4 - 1 = 15 \) comparators, which makes option (A) correct.

Step 1: Option (A) is correct because 15 comparators are required for a 4-bit Flash ADC.

Step 2: Option (B) is incorrect because the ADC requires more than just a 4 to 2 encoder. It needs a large priority encoder depending on the number of comparators.

Step 3: Option (C) is incorrect because a change in \( \frac{V}{16} \) would affect the LSB, not the MSB.

Step 4: Option (D) is correct because a change in \( \frac{V}{16} \) affects the least significant bit (LSB) of the output.
Thus, the correct answers are (A) and (D).

Final Answer: (A) The ADC requires 15 comparators, (D) A change in the input voltage by \( \frac{V}{16} \) will always flip the LSB of the output.