CUET PG 2026 — Computer PYQ

Solution

A T (Toggle) Flip-Flop is a circuit that changes its output state (toggles) every time it receives a high input ($T=1$) and a clock pulse. To convert a JK Flip-Flop into a T Flip-Flop, we must look at how the JK inputs behave:

1. JK Truth Table behaviors:

   • When $J=0,K=0$, the state remains unchanged (No change).

   • When $J=1,K=1$, the state always toggles ($Q_{n+1}=\overline{Q_n}$).

2. Conversion Logic:

   To get a T Flip-Flop, we tie the $J$ and $K$ inputs together.

   • If $T=0$, then $J=0$ and $K=0$ (No change).

   • If $T=1$, then $J=1$ and $K=1$ (Toggle).

3. Characteristic Equation:

   The characteristic equation for a JK Flip-Flop is:

   $$Q_{n+1}=J\overline{Q_n}+\overline{K}{Q}_n$$

   By setting $J=K=T$, it becomes the T Flip-Flop equation:

   $$Q_{n+1}=T\overline{Q_n}+\overline{T}{Q}_n=T\oplus Q_n$$

Conclusion:

A JK flip-flop behaves as a T flip-flop when both inputs $J$ and $K$ are connected together. Among the given options, the state where the JK flip-flop performs the "Toggle" function (the core characteristic of a T flip-flop) is when both inputs are high.

Correct Option: (b) $J=1,K=1$