Question

In the case of a 4-bit ripple counter, if the time period of the waveform at the last flip-flop is 64 microseconds, what is the input frequency?

• A. 250 KHz
• B. 125 KHz
• C. 500 KHz
• D. 2 KHz

Hint:

In ripple counters, the input frequency is related to the frequency at the last flip-flop by a factor of \( 2^n \), where \( n \) is the number of bits in the counter.

Answer 1

The Correct Option is A

Step 1: Understanding the ripple counter.

In a ripple counter, the output of each flip-flop is connected to the clock input of the next flip-flop. A 4-bit ripple counter will have 4 flip-flops, and each flip-flop toggles its state at half the frequency of the previous one.

Step 2: Relationship between the input and output frequency.

If the time period of the waveform at the last flip-flop is 64 microseconds, it means the frequency of the last flip-flop is: \[ f_{last} = \frac{1}{64 \, \mu\text{s}} = \frac{1}{64 \times 10^{-6}} = 15.625 \, \text{kHz} \]

Since each flip-flop divides the frequency by 2, the input frequency is: \[ f_{input} = 15.625 \, \text{kHz} \times 2^4 = 15.625 \, \text{kHz} \times 16 = 250 \, \text{kHz} \]

Thus, the correct answer is \( 250 \, \text{KHz} \).