CS302 Final Term Short Notes

CS302 Final Term Short Notes

Q1. Define sequential circuit?

Answer: Digital circuit that use memory element for their operation is known as sequential circuit.

Q2. Define latches?

Answer: A latch is a temporary storage device that has two stable states. A latch output can change from one state to the other by applying appropriate inputs.

Q3. Define bi-stable multivibrators?

Answer: Flip-Flops are synchronous bi-stable devices, known as bi-stable multivibrator.

Q4. which flip-flops are used in digital logic circuit?

Answer: There are generally three types of flip-flops are used in digital circuit. These are as under. i. S-R edge-triggered flip-flop ii. D edge-triggered flip-flop iii. J-K edge-triggered flip-flop

Q5. Why S-R, J-K and D inputs are known as synchronous inputs?

Answer: S-R, J-K and D inputs are known as synchronous because the outputs change when appropriate input values are applied at the inputs and clock signal is applied at the clock input.

Q6. what are the flip-flop operating characteristics?

Answer: There are the following characteristics if flip-flop. These are as under:

1. Propagation Delay
2. Set-up time
3. Hold time
4. Maximum clock frequency
5. Pulse width
6. Power Dissipation

Q7. Define propagation delay?

Answer: The propagation delay is the time interval of time when the input is applied and the output changes.

Q8. Define set-up time?

Answer: When a clock transition occurs at the clock input of a flip-flop the output of the flip-flop is set to a new state based on the inputs.

Q9. Define hold time?

Answer: The input signal maintained at the flip-flop input has to be maintained for a minimum time after the clock transition for the flipflop to reliably clock in the input signal. The minimum time for which the input signal has to be maintained at the input is the Hold time of the flip-flop.

Q10. Define maximum clock frequency?

Answer: A flip-flop can be operated at a certain clock frequency. If the clock frequency is increased beyond a certain limit the flip-flop will be unable to respond to the fast changing clock transitions, therefore the flip-flop will be unable to function. The maximum clock frequency fmax is the highest rate at which the flip-flop operates reliably.

Q11. Define pulse width?

Answer: A flip-flop uses the clock, preset and clear inputs for its operation. Each signal has to be of a specified duration for correct operation of the flip-flop. The manufacturer specifies the minimum pulse width tw for each of the three signals. The clock signal is specified by minimum high time and minimum low time.

Q12. Define power dissipation?

Answer: A flip-flop consumes power during its operation. The power consumed by a flip-flop is defined by P = Vcc X Icc. The flip-flop is connected to +5 volts and it draws 5mA of current during its operation, therefore the power dissipation of the flip-flop is 25 mW.

Q13. Define 555 timer?

Answer: The 555 Timer is a versatile and widely used device which can be configured as a mono-stable One-Shot or as an Astable multivibrator. An Astable multivibrator is known as an Oscillator which does not have any stable state.

Q14. Define Clock skews?

Answer: One of the most common problems in synchronous circuits is ‘Clock Skew’. One type of Clock Skew occurs when the same clock signal arrives at different times at different clock inputs to propagation delay, which causes different flip-flops to change states asynchronously leading to unpredictable outputs.