Propagation Delay Calculation for a MOD-30 Ripple Counter

Given:
- MOD-30 ripple counter
- Maximum operating frequency: 8 MHz

To Find:
- Propagation delay of each flip flop

Explanation:

A MOD-30 ripple counter has a total of 30 states, which means it will cycle through all the states from 0 to 29 before resetting to 0. Each flip flop in the counter will divide the input frequency by 2, so the overall frequency of the counter will be the input frequency divided by 2^n, where n is the number of flip flops.

Step 1: Calculate the Number of Flip Flops:
To find the number of flip flops required for a MOD-30 ripple counter, we need to calculate the minimum value of n that satisfies the equation 2^n >= 30.

2^4 = 16 (not enough)
2^5 = 32 (satisfies the condition)

Therefore, a MOD-30 ripple counter will require 5 flip flops.

Step 2: Calculate the Overall Frequency:
The overall frequency of the counter can be calculated using the formula:

Overall Frequency = Input Frequency / 2^n

For a MOD-30 ripple counter with 5 flip flops, the overall frequency will be:

Overall Frequency = 8 MHz / 2^5
= 8 MHz / 32
= 250 kHz

Step 3: Calculate the Propagation Delay:
The propagation delay of each flip flop can be calculated using the formula:

Propagation Delay = 1 / Overall Frequency

Propagation Delay = 1 / 250 kHz
= 4 microseconds
= 4000 nanoseconds

However, the correct answer is given as 25 nanoseconds, so it seems there might be a mistake in the question or answer choices. The calculated propagation delay is significantly higher than 25 nanoseconds.

Therefore, it is recommended to double-check the question or consult the source material for the correct answer.