Skip to content

SR Flip Flop Working Explained with NAND Gates and Clock

SR Flip Flop Working Principle

This video explains the SR flip flop circuit, showing how it differs from the SR latch by adding a clock signal and two additional NAND gates for edge-triggered operation. For a foundational understanding of the basic memory element that precedes this design, see Understanding Gated SR Latches: Operation and Applications Explained.

Circuit Setup

  • The SR flip flop is built by extending the SR latch (which uses two cross-coupled NAND gates).
  • Two extra NAND gates are added at the inputs to connect the clock signal.
  • The inputs are S (Set) and R (Reset), and the clock acts as the control signal.

Key Behavior

  • Without Clock: If the clock is not applied (0), the circuit remains in its previous state (no change). The output Q holds its value.
  • With Clock (Triggered): When the clock is set to 1, the flip flop is enabled and responds to the S and R inputs.

Working for Each Input State (with Clock)

State 1: S=0, R=0 (Hold State)

  • When S=0 and R=0, the NAND gates produce the same output as before.
  • The circuit holds its previous state (Q remains unchanged).

State 2: S=1, R=0 (Set State)

  • S=1 sets the output Q to 1.
  • The NAND gates propagate this value, and the complementary output Q̅ becomes 0.

State 3: S=0, R=1 (Reset State)

  • R=1 forces the output Q to 0.
  • The NAND gates produce Q=0 and Q̅=1.

State 4: S=1, R=1 (Invalid State)

  • When both inputs are 1, the outputs become unpredictable (both 0 or both 1).
  • This is called the invalid or forbidden state and should be avoided.

Important Notes

  • The SR flip flop is a sequential circuit that uses feedback from its outputs to maintain state.
  • The clock signal controls when the inputs are processed, making it a synchronous device. To explore how this concept evolves into more robust designs, read about Understanding Clocked D Latches and Edge-Triggered Flip-Flops.
  • The SR latch's invalid condition (S=1, R=1) remains invalid in the SR flip flop.

Key Takeaway: The SR flip flop works like the SR latch but with a clock gate that only updates the output when the clock is high. Mastering these four states is essential for understanding more complex flip flops.

For a deeper dive into how this design is refined to eliminate timing issues and the invalid state, see Master-Slave D-Type Flip-Flops: Ensuring Reliable Digital Circuit Timing.

Keep this summary

Save it to LunaNotes and it becomes a real note in your library — editable, searchable, and ready to turn into flashcards or a diagram. Free to start.

Save to LunaNotes

Or summarise for another video.

32K+ people have turned 65K+ videos into notes

“Very useful tool. I'm using it for the last couple weeks and I'm loving it so far. Makes learning on YouTube a great experience.”
Bhai Chrome Web Store review

This summary and transcript were automatically generated using AI with the Free YouTube transcript summary tool by LunaNotes.

Related summaries

Understanding Gated SR Latches: Operation and Applications Explained

Understanding Gated SR Latches: Operation and Applications Explained

Explore how gated SR latches enhance control in digital circuits by enabling state changes only when permitted. This guide covers the design differences between NOR and NAND based gated SR latches, their timing behavior, and practical uses such as independent room cooling control in air conditioning systems.

Understanding Gated Dlatches: One-Bit Memory Devices Explained

Understanding Gated Dlatches: One-Bit Memory Devices Explained

This article explains the construction and operation of gated Dlatches, built from gated SR latches, and explores their behavior using timing diagrams. Learn how Dlatches function as one-bit memory devices, their advantages over SR latches, and their applications in data storage and transfer.

Understanding Clocked D Latches and Edge-Triggered Flip-Flops

Understanding Clocked D Latches and Edge-Triggered Flip-Flops

Explore the operation and enhancements of clocked D latches, including edge detection for precise timing control. Learn how these devices synchronize data storage in digital circuits and their role in memory and counter applications.

Master-Slave D-Type Flip-Flops: Ensuring Reliable Digital Circuit Timing

Master-Slave D-Type Flip-Flops: Ensuring Reliable Digital Circuit Timing

This summary explains the importance of clock synchronization in digital circuits and how propagation delays affect circuit stability. It details the design and function of master-slave D-type flip-flops, illustrating how they prevent glitches and ensure data integrity across clock cycles.

Understanding Boolean Functions: Sum of Products and Product of Sums

Understanding Boolean Functions: Sum of Products and Product of Sums

This video tutorial explains how to represent Boolean functions in both Sum of Products (SOP) and Product of Sums (POS) forms. It covers the concepts of minterms and maxterms, providing examples and clarifying the differences between canonical and non-canonical forms.

Found this summary useful?

Take it with you. One click puts it in your own LunaNotes library.

Save to LunaNotes

Start taking better notes today with LunaNotes