Question

The maximum clock frequency in MHz of a 4-stage ripple counter, utilizing flip-flops, with each flip-flop having a propagation delay of 20 ns, is _________. (round off to one decimal place)

Hint:

For a ripple counter, the maximum clock frequency is limited by the total propagation delay of all flip-flops in the counter.

Answer 1

Correct Answer: 12.3

The maximum clock frequency \( f_{max} \) for a ripple counter is determined by the propagation delay of the flip-flops. For a 4-stage ripple counter, the total propagation delay is the sum of the individual delays: \[ \text{Total delay} = 4 \times 20 \, \text{ns} = 80 \, \text{ns} \] The maximum clock frequency is the reciprocal of the total propagation delay: \[ f_{max} = \frac{1}{\text{Total delay}} = \frac{1}{80 \, \text{ns}} = \frac{1}{80 \times 10^{-9}} = 12.5 \, \text{MHz} \] Thus, the maximum clock frequency is \( 12.5 \, \text{MHz} \).