Why does the circuit not simulate correctly when i put two circuits in the same design.

[08Ultrasound]

Hi,

I have two circuits that i can simulate in their own designs and they work correctly but when i put the two circuits within the same design, one circuit does not work. I don't understand why this is happening. Could someone please explain why this is happening and how to solve it please?

Below is the circuit i'm attempting to simulate. Each little circuit is what i've made previously in their own designs.

When i simulate each circuit in it's own design i get the following waveforms.

When i simulate both of the circuits together i get the following waveforms. The yellow and red signals have been attached to the right hand side of the 10nF caps. The signals have also been offset.

Thanks for any help.

[Tien_P]

Hi Ultrasound,

Please post the Multisim circuit file, there are settings in the circuit file that can not be view on the schematic.

[08Ultrasound]

By the Multisim circuit file do you mean the .ms12 file? If so, i've attached a copy of it here.

[08Ultrasound]

And here are the circuits individually.

[08Ultrasound]

I thought i had uploaded both individual circuits. This is the one that didn't upload.

[Tien_P]

Hi,

You used VCC in both circuits and both have different values, when you combined the circuits only one circuit have the correct VCC value.  To get around this change one of your source VCC1.