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Digital Circuit System Lab Experiments

To design ripple counter using J-K Flip-Flop



Aim

To design ripple counter using J-K Flip-Flop

Apparatus Required:

Digital trainer kit, IC 7476, Connecting wires.

Theory

A counter is a sequential circuit that moves through a predefined sequence of states upon applying of clock pulses. The sequence of states may follow the binary number sequence or an arbitrary manner (no sequence). The simplest example of a counter is the binary counter which follows the binary number sequence. An n-bit binary counter contains n flip-flops and can count binary numbers from 0 to (2n -1). Counters are classified into two types: synchronous counters and asynchronous/ripple counter. In a synchronous counter, all flip flops are triggered by a common pulse (CLK). In the ripple counter a flip flop output used as a signal for triggering other flipflop.

Ripple Counter (Asynchronous)

A ripple counter is a serial counter. The clock input is applied to only the first of the series of the Flip Flop. Clock pulses for the other Flip Flop come from the preceding Flip Flop. Thus, the clock pulse “ripple” through the circuit in a series fashion. Such circuit is also called asynchronous since the only pulse required for the operation is the clock pulse. The JK Flip Flop have the J and K inputs both tied high, which allows them to toggle with each inputpulse.

3-bit-ripple-counter
pin-diagram-of-ic-7476
CLK QC QB QA
0 0 0 0
1 0 0 1
2 0 1 0
3 0 1 1
4 1 0 0
5 1 0 1
6 1 1 0
7 1 1 1
8 0 0 0

output-waveform

Procedure:-

  1. Place the breadboard gently on the observationtable.
  2. Fix the IC which is under observation between the half shadow lineof breadboard, so there is no shortage ofvoltage.
  3. Connections are made as per the circuitdiagram
  4. Switch on the powersupply.
  5. Apply clock pulses at clock input of IC and note the outputs after each clock pulse. O/Pis observed at QA, QB & QC for IC7476.

Precautions:

  1. All ICs should be checked before starting theexperiment.
  2. All the connection should betight.
  3. Always connect ground first and then connectVcc
  4. Suitable type wire should be used for different types ofcircuit
  5. The kit should be off before changing theconnections.
  6. After the completion of experiment, switch off the supply of the apparatus

Result:Ripple counter using J-K Flip-Flop is designed and its truth table isverified.

Questions:

Q1:What is an asynchronouscounter?

Ans:Asynchronous counter is one in which flip flops are connected in such a way that the first flip flop output is the clock for the nest flip flop.

Q2:What is the major drawback of asynchronouscounters?

Ans:High frequency applications are limited because of internal propagation delay.

Q3:How many different states 2 bit asynchronous counters have?

Ans:

Q4:How the up counter can be made to work as a downcounter?

Ans:By taking the counter outputs Q’ instead of Q the up counter can be made to work as a down counter.