How to Flip Flop Using Discrete Components

If you don't have a flip-flop in your electronic tool box, you can always build one with a few discrete digital logic components, such as AND, NAND, OR, NOR and inverter components. With these basic components you can build a wide variety of flip-flops such as RS, JK and toggle flip-flops. You can even add functions to each flip-flop such as resets, sets and multiple outputs. Constructing an R-S flip-flop is a good place to start if you want to make flip-flops from discrete components. It takes two NAND gates to make one.

Things You'll Need

  • Two NAND gates
  • Electronic breadboard
  • Three power supplies
  • Digital voltmeter
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Instructions

    • 1

      Call the first two-input NAND gate component NAND1. Call its output NAND1_OUT, its first input NAND1_IN1 and its second input NAND1_IN2. Call the second two-input NAND gate component NAND2. Call its output NAND2_OUT, its first input NAND2_IN1 and its second input NAND2_IN2.

    • 2

      Connect NAND1_OUT to NAND2_IN2. Connect NAND2_OUT to NAND1_IN2. Connect your voltmeter positive lead to NAND1_OUT and its negative lead to the negative lead of the first power supply. Call the first power supply "power supply one," the second one "power supply two" and the third one "power supply three." Set your voltmeter scale to 10 volts.

    • 3

      Set the voltage output level of power supply one to 0 volts. Set the voltage output level of power supply two to 0 volts. Set the voltage output level of power supply three to 5 volts. Turn off your power supplies.

    • 4

      Connect the positive lead of the first power supply to NAND1_IN1. Connect the negative lead of the first power supply to the ground pin of NAND1_IN1. Connect the ground pin of NAND1_IN1 to the ground pin of NAND2_IN1. Connect the positive lead of the second power supply to NAND2_IN1. Connect the negative lead of the second power supply to the negative lead of the first power supply.

    • 5

      Turn on your power supplies. Measure the voltage at the pin called NAND1_OUT. Verify that it reads 5 volts.

    • 6

      Increase the voltage level of power supply two to 5 volts and observe the display on the voltmeter. Verify that the voltage at NAND1_OUT has changed to 0 volts and you have made your discrete components flip-flop from 5 volts to 0 volts. Now set power supply one to 5 volts and power supply two to 0 volts. Verify that the voltage at NAND1_OUT has changed to 5 volts and that you have made your discrete components flip-flop from 0 volts to 5 volts.

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