Multisim and Ultiboard

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"negative logic" I cannot get it to simulate in Multisim


Hi All

I've been lurking around these support pages, finding solutions to my design problems, for a couple of years. However, I cannot find a solution for this one.

I'm powering a 74HC04 hex inverter with -5v on pin 7 and 0v on pin 14. I need the -5v to drive an RF switch.

The circuit works on the bench but I cannot get it to simulate in Multisim. I did find information on the hidden pins, and made some changes, with no success.

I've attached a screenshot of the circuit.

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Hi jampitt,


When you simulate the circuit is something that is not working as expected? Or it is not working at all? Do you have an error?


What type of changes you made on the model? Did you change the Spice model?

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Hi miraquesa

Thanks for taking an interest in this.

When I simulate, I am expecting to see complimentary pulses from 0 to -5V. What I get is the first inverter stuck  at 0V and the second inverter is stuck at -5V. On the screen shot provided, the top red trace is the TTL input pulse. The second green trace is the 0 to -5V input to the inverters. The two lower traces are the inverter outputs.

I get no errors.

I have changed the hidden pins to pin 7 = -5V and pin 14 = 0V.

I don't think the model is all it could be.

Regards, Jim

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