D-type frequency divider
- using a logic D-type flip flop electronic circuit to provide a
frequency division of two
The D-type logic flip flop is a very versatile circuit. It
can be used in many areas where an edge triggered circuit is needed. In one
application this logic or digital circuit provides a very easy method of
dividing an incoming pulse train by a factor of two.
The divide by two circuit employs one logic d-type element.
Simply by entering the pulse train into the clock circuit, and connecting the
Qbar output to the D input, the output can then be taken from the Q connection
on the D-type.
D-type frequency divide by two circuit
The circuit operates in a simple way. The incoming pulse
train acts as a clock for the device, and the data that is on the D input is
then clocked through to the output. To see exactly how the circuit works it is
worth examining what happens at each stage of the waveforms shown below. Take
the situation when the Q output is a level '1'. This means that the Qbar output
will be at '0'. This data is clocked through to the output Q on the next
positive going edge from the incoming pulse train on the clock input. At this
point the output changes from a '1' to a '0'. At the next positive going clock
pulse, the data on the Qbar output is again clocked through. As it is now a '1'
(opposite to the Q output), this is transferred to the output, and the output
again changes state.
D-type frequency divide by two circuit
It can be seen that the output of the circuit only changes
state on the positive going edges of the incoming pulse clock stream. Each
positive edge occurs once every cycle, but as the output of the D type requires
two changes to complete a cycle, it means that the output from the D-type
circuit changes at half the rate of the incoming pulse train. In other words it
ahs been divided by two.
There are some precautions when using this type of circuit.
The first is that the pulse train should have sharp edges. If the rising edges
are insufficiently sharp then there may be problems with the circuit operating
as it should. If this is the case, then the problem can be easily overcome by
simply placing an inverter before the clock input. This has the effect of
sharpening the edges on the incoming signal.
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