*Question E7A04:
How many flip-flops are required to divide a signal frequency by 16?*  

*Correct Answer is  A: 4*  

### AI Response: (may contain errors)  

To determine how many flip-flops are required to divide a signal frequency by a certain factor, you can use the following rule:

- Each flip-flop divides the frequency by 2.

Therefore, to divide a signal frequency by 16, you need to find how many times you can divide 16 by 2:

1. Start with 16 and divide by 2 repeatedly:
   - $16 \div 2 = 8$
   - $8 \div 2 = 4$
   - $4 \div 2 = 2$
   - $2 \div 2 = 1$

2. You divided by 2 a total of 4 times to reach 1.

Thus, you need 4 flip-flops to divide the frequency by 16.

### Explanation of Choices:
- **A: 4**  
  Correct. As shown above, 4 flip-flops are required to divide the frequency by 16.

- **B: 6**  
  Incorrect. 6 flip-flops would divide the frequency by $2^6 = 64$, which is more than needed.

- **C: 8**  
  Incorrect. 8 flip-flops would divide the frequency by $2^8 = 256$, which is much more than needed.

- **D: 16**  
  Incorrect. 16 flip-flops would divide the frequency by $2^{16} = 65536$, which is far more than needed.

### Useful Formula:
To find the number of flip-flops ($n$) needed to divide by a factor ($F$), use the formula:
$$
n = \log_2(F)
$$
For $F = 16$, $n = \log_2(16) = 4$.