Oh, I'll take the suggestion, thank you very much for recommend the software and for the help!

 

hi D,
If you would like to get more information on LTSpice there is a user Group.
https://groups.io/g/LTspice

also info here
https://forum.allaboutcircuits.com/...-of-ltspice-free-download.133690/post-1112695


E

 

An old fashioned TTL gate simulated in old fashioned Multisim?
I used TTL 50 years ago! I have never seen Multisim except from students in these forums.

The PN base-collector junctions of the input transistors that have the switches turned off cause the inputs to be a logic high.
Ohms Law shows that a red LED will have its current limited by the 130 ohms output resistor and diode to about 120mA.

 

Hello guys, I'm doing the logic gate OR, I simulated it on Multisim but I amn't obtaining the correct truth table, with all the inputs I obtained the turn ON LED. Am I doing something wrong?, thank you. (I take the circuit from the Datasheet of SN7432)

View attachment 219380View attachment 219381

make the truth table and do it again

 

The output of an OR gate goes high if one or more inputs are high. If one or both of your input switches are turned off then the LED will turn on.

 

I see a join between R2 and Q5 that shouldn’t be there.
The circuit relies on the current in the base-collector diode of Q1 and Q4 to work. Can the simulator cope with that?

 

In my opinion in the scheme Multisim there is an extra connection - bases Q4 and Q5 are connected!

 

In my schematics I make wires jump high over other wires, and use BIG solder joint dots.