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SN7400: Time conTrolled switch problem in TINA TI

Part Number: SN7400

I am using TINA TI for simulation but there is a time-controlled switch that is not showing the result properly in steady-state.



  • Hello Vanaraj,

    The simulation output is correct.

    Your input is a constant 3.5V (HIGH to a TTL input), so the output is a constant 'LOW' (200mV).  The series switch doesn't change the voltage at VF1 regardless of the impedance (your settings are for 0ohm when on, 1Gohm when off).  The current into VF1 is zero, so the current through the switch is zero (Kirchhoff's Current Law) -- regardless of the resistance of the switch there will be no voltage drop with no current (Ohm's Law).

    If you want to see a change at the output due to the switch changing state, then you must apply a load. In this case, I applied a 1Mohm resistor divider, which should make the output 2.5V when the switch is open, and allow the output to drive the line to 200mV when the switch is closed: