Flip-Flops Explained – Types, Truth Tables
Flip flop:
A flip-flop is a sequential digital electronic circuit
having two stable states that can be used to store one bit of binary data.
Flip-flops are the fundamental building blocks of all memory devices.
Types of flip flop:
1. S-R flip flop
2. J-K flip flop
3. D flip flop
4. T flip flop
S-R flip flop:
This is the simplest flip-flop circuit. It has a set input
(S) and a reset input (R). When in this circuit when S is set as active, the
output Q would be high and the Q' will be low. If R is set to active then the
output Q is low and the Q' is high. Once the outputs are established, the
results of the circuit are maintained until S or R get changed, or the power is
turned off.
Truth Table of S-R Flip-Flop
J-K flip flop:
Because of the invalid state corresponding to S=R=1 in the
SR flip-flop, there is a need of another flip-flop. The JK flip-flop operates
with only positive or negative clock transitions. The operation of the JK
flip-flop is similar to the SR flip-flop. When the input J and K are different
then the output Q takes the value of J at the next clock edge.
When J and K both are low then NO change occurs at the
output. If both J and K are high, then at the clock edge, the output will
toggle from one state to the other.
Truth table of J-K flip flop:
D flip flop:
In a D flip-flop, the output can only be changed at positive or negative clock
transitions, and when the inputs changed at other times, the output will remain
unaffected. The D flip-flops are generally used for shift-registers and
counters. The change in output state of D flip-flop depends upon the active
transition of clock. The output (Q) is same as input and changes only at active
transition of clock
Truth table of D flip flop
T flip flop:
A T flip-flop (Toggle Flip-flop) is a simplified version of
JK flip-flop. The T flop is obtained by connecting the J and K inputs together.
The flip-flop has one input terminal and clock input. These flip-flops are said
to be T flip-flops because of their ability to toggle the input state. Toggle
flip-flops are mostly used in counters
Truth table of T flip flop
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