74LS74 Dual D Flip-Flop: How to Use it?

74LS74 Pinout

74LS74 Symbol

74LS74 Footprint

74LS74 3D Model

• Dual D Flip Flop Package IC

• Operating Voltage: 2V to 15V

• Propagation Delay: 40nS

• Minimum High-Level Input Voltage: 2 V

• Maximum Low-Level Input Voltage: 0.8V

• Operating Temperature: 0 to 70°C

• High-Level Output Current: 8mA

• Available in 14-pin SO-14, SOT42 packages

• Used as Shift Registers

• Memory/Control Registers

• Buffer Circuits

• Sampling Circuits

• Latching devices

The equivalents for 74LS74:

• 74LVC2G80

• HEF40312B

74LS74 dual d flip-flop contains two independent positive-edge-triggered D flip-flops with complementary outputs. The information on the D input is accepted by the flip-flops on the positive-going edge of the clock pulse. The triggering occurs at a voltage level and is not directly related to the transition time of the rising edge of the clock. The data on the D input may be changed while the clock is LOW or HIGH without affecting the outputs as long as the data setup and hold times are not violated. A low logic level on the preset or clear inputs will set or reset the outputs regardless of the logic levels of the other inputs.

It is rather simple to use a Flip-Flop. Simply use the Vcc and GND pins to power the IC. As previously stated, each flip-flop works separately; simply connect the input signals 2 and 3 to use the first flip-flop, and the output will be at pins 5 and 6. A clock source should be given for pin 3, which is usually a PWM signal from an MCU or 555 timers. By making the pin high, you can clear the data and reset the flip flop. Taking a look at the function table below will help you understand how the Flip flop works. The symbol "X" stands for "don't care," while the up-arrow represents the signal's rising edge.

You can also run a simulation of the IC to see if it performs as expected. I've used logic state and logic bits to see if the IC works as it should, but you could use actual circuitry from your application to see if it meets your requirements. The gif file below can be compared to the truth table above to ensure that the IC is functioning properly.

How to use 74LS74

74LS74 Connection Diagram

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