Adding a semiconductor causes the simulation to stop working

[dingebre]

In a related post, I got my simple UJT circuit working.

So, now I want to add some additional circuitry to modify and/or use the output of the UJT oscillator for different applications. I found that when I add any kind of semiconductor; diode, transistor, etc., the UJT circuit stops oscillating.

This came up when I was trying to add a simple "shaper" circuit to turn the UJT saw wave into a square wave. When I take the "shaper" circuit on its own in a different design, the circuit works great and shapes a sawtooth wave to a square wave as wanted. When I add the circuit to the UJT, the UJT stops oscillating. If I delete all the semiconductors in the shaper, the UJT works.

This happens whether or not the two circuits are connected in any way. I can add passive components, but if I add a semiconductor, it stops.

I am attaching the two circuits. The extra circuit piece in the UJT trigger design is left over from when I was trying to see which component and/or block was causing the malfunction.

Thanks 

[OStep]

...interesting case. I am investigating why that is.

A quick workaround is to set the Initial Conditions to "Set to zero" (under Simulation/Interactive Simulation Settings)

[dingebre]

Thank you Max. I'll be interested to hear why when you figure it out.

In the meantime, I'm back from my business trip and have some time to give your suggestion a try.

David 

[rzolnowski]

I am having the same problem.  Set up an oscillator circuit using a 5 mhz crystal (Colpitts) and it works fine.  Added an ampliciation stage (2n3904) and the orginal circuit would not oscillate.  When I remove the 2n3904  from the worksheet the intial circuit will again oscillate.  If I put the 2n3904 back on the sheet and tie all of the pins together the original circuit will oscillate...obviously not very useful!