3-Bit and 4-Bit Ripple Counters

3-Bit and 4-Bit Ripple Counters work as same the 2-Bit ripple-counters work. There is the only difference between them which is the number of flip-flops. And also the number of states due to the addition of flip-flops. The 2 bit asynchronous counter uses 2 flip-flops. And on the other hand, 3-Bit uses 3 flip-flops and 4-Bit counter uses 4 flip-flops.

3-Bit Asynchronous Counter

We already know that it works the same as the 2-Bit Asynchronous Counter. But there is a change in the number of states. The number of states in this counter is eight because of the third flip-flop. As 2n = 23 finally becomes 8 no. of states.
The figure below is a 3-Bit Asynchronous counter along with its timing diagram for one cycle.

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4-Bit Asynchronous Counter

It works the same as the previous two i.e. 2-bit and 3-bit counters. As stated earlier in the 3-bit counter about the change in the number of states, 4- bit counter acquires it too. There are 16 numbers of states due to the fourth flip-flop here. This happens as per the rule i.e. 2n = 24 = 16.

The figure along with the timing diagram of 4 bit counter is given below:

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Propagation Delay

The asynchronous counters are referred to as the ripple-counters because of the following reasons:

• All subsequent flip-flops are clocked by the output of the preceding flip-flop.
• The first clock pulse is experienced by the first flip-flop. This does not go to the second flip-flop immediately due to the propagation delay of the first. Because of this delay between the two flip-flops in a counter, it is called the propagation delay. Again, there is a propagation delay through the second before the third one can be triggered.
• This phenomenon creates a ruffle through the counter. Due to this, it takes some time for the propagation to reach the data to the last flip-flop.

That is why the asynchronous counter is called the ripple counter.