Unit 4: Principles of Electrical and Electronic
Engineering
LO6: Understanding digital electronics
– D type bistable flip-flop
Student activity sheet
Activity 1
The symbol below is for a D type flip-flop (that is positive edge triggered).
D
Q
CK
Q
Begin this activity by investigating the function and operation of the D type flip-flop. Here are some
things for you to consider:



How does the flip-flop operate and what is its purpose?
What are each of the inputs and outputs?
In what type of applications are flip-flops used?
Activity 2
The flip-flop shown is a positive edge triggered device meaning that the input signal (D) is captured on
positive transitions of the clock signal (CK).
Look at the timing diagrams in problem 1 to problem 3 and identify the positive transitions of the clock
(CK) waveform.
Use this to complete the diagrams to show the output signals (Q and
December 2014
).
Problem 1
Logic 1
D
Positive Edge
CK
Q
Q
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Logic 0
Problem 2
D
CK
Q
Q
December 2014
Problem 3
D
CK
Q
Q
December 2014
Activity 3
The symbol for another D type flip-flop is shown below. This is a negative edge triggered D type flip-flop
– with the input signal on D being captured on negative transitions of the clock signal (CK).
D
Q
CK
Q
Identify the negative edges of the clock waveform (CK) shown in the timing diagrams for problem 4 to
problem 6 and complete the corresponding output signals (Q and
December 2014
).
Problem 4
Logic 1
D
Negative Edge
CK
Q
Q
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Logic 0
Problem 5
D
CK
Q
Q
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Problem 6
D
CK
Q
Q
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Activity 4
A good way to test the operation of a flip-flop is to build a circuit or run a computer-based simulation.
If you have access to practical resources, build and test a flip-flop circuit using a D type flip-flop.
The following web link contains a simulation of a D type flip in operation. The website is free but you will
need to set yourself up with a user name and password to run the simulation.
http://www.docircuits.com/public-circuit/457/d-flipflop
Run the simulation and analyse the results (the timing diagram).
Does this D type circuit function as expected?
What is the function of the S and R input pins on this flip-flop?
December 2014