To know about T Flip Flop we have to know the meaning of T in T Flip Flop. The T stands for toggle that means T flip Flop stands for toggle Flip Flop. As name suggests this flip flop is only use the toggle state property.as we know this toggle property only has in JK flip flop. So with a slight modification of a J-K flip-flop, we can construct a new flip-flop called a T flip flop. If the two inputs J and K of a J-K flip-flop are tied together it is referred to as a T flip-flop. Hence, a T flip-flop has only one input T and two outputs Q and Q’. The name T flip-flop actually indicates the fact that the flip-flop has the ability to toggle. It has actually only two states—toggle state and memory state. Since there are only two states, a T flip flop is a very good option to use in counter design and in sequential circuits design where switching an operation is required. The truth table of a T flip-flop is given in bellow.
Now question is how is the circuit look like and how we can build with using JK Flip Flop ? See at bellow the circuit diagram of T Flip Flop.
If the T input is in 0 state (i.e., J = K = 0) prior to a clock pulse, the Q output will not change with the clock pulse because we know for JK Flip Flop J = K =0 output will be no change. On the other hand, if the T input is in 1 state (i.e., J = K = 1) prior to a clock pulse, the Q output will change to Q’ with the clock pulse because we know for JK Flip Flop J = K = 1 output will be toggle. In other words, we may say that, if T = 1 and the device is clocked, and then the output toggles its state.
The truth table shows that when T = 0, then Qn+1 = Qn, i.e., the next state is the same as the present state and no change occurs. When T = 1, then Qn+1 = Q’n, i.e., the state of the flip-flop is complemented.