# Circuit simulation to reverse engineer a IC

Is it possible to create circuit simulation in KiCad to place theoretical components to build a circuit?

Yes, of course.
Draw the schematic in KiCAD using real parts (eg, BC847/857, 1N4148 etc.) and run the simulation.
Nice little circuit, by the way. In practice, itâ€™s a lower voltage DIAC.

Thousand \$ question is that this is an IC and it needs to be built as discrete components.

Plenty of packages I havenâ€™t seen for a long time!

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IC08040 is dead and must be replaced

From the package drawings, Iâ€™d say that IG04080 is a hybrid, not an IC. Should be possible to reproduce.

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Where to begin with this project?

See my first post. Easy.

This is going circular.
1: do what you proposed and draw/simulate it using discrete parts.
2: hire a consultant that will do it for you.
End.

The rest is about electronic design, which might be more appropriate for eevblog.com or other electronic design sites.

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I believe I may have it

That is the basic circuit,
Now I need to define the Zener values - how?
Define voltage values - how?
Defne R values - mystery values
How to create a simulation?

How much of the surrounding circuits do I need to add?

I used the following procedure to test the special Yamaha Silicon Bilateral Switch IG04080. It must be removed from the circuit board to test it. Use a bench power supply set at 12v, and put a 10k to 20k resistor in series with the positive output of the supply. (Assume you select a 12k resistor in series with the 12v supply)

1. Connect the cold end of the 12k resistor to pins T1 and G on the IG04080. Connect the T2 pin to GND on the bench supply. With a voltmeter from T1/G to T2, it should show around 8v. Mine was 8.00v. I had expected about 9v, but 8v is better, and it is what it is.

2. Reverse the connection of T1/G and T2. Connect the 12k resistor to T2 and ground T1/G. Again it should read 8v across the IG04080. Mine was 7.99V. This is amazingly close matching by the way.

3. Connect the cold end of the 12k resistor to the T1 pin alone. Leave the G pin open circuit. Connect T2 to GND. Measure the voltage across T1 to T2. I expected it to be around 2.1v. Mine was around 1.3v.

4. Reverse the connection of T1 and T2 leaving G open again. The result should be essentially the same as step 3 above.

This procedure tests the internal diode bridge and Zener regulator first. Then tests the internal â€śSCRâ€ť breakover voltage. I believe that if the device under test passes this procedure, that it can be deemed to be OK.

Posted to eevblog as per your recommendation

Not too sure it has been answered.