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I claim no prizes whatever for my getit2 circuit, but can anyone explain this? Stop time 0.01S Step time 0.00001S Output NODE5 Time domain simulation gives me what appears to be rubbish. BUT add add NODE9 as an output and it's ok. I have a feeling the problem is perhaps more to do with displaying the result rather than the simulation itself.

Well there's several problems.

(1) When you get funny results, try putting a 100 ohm resistor in the base of the 3904. In real life and in simulation, that stops a lot of VHF oscillations.

(2) If it still oscillates, try a small capacitor from collector to base. In this circuit. a 0.001uf capacitor from 3904 collector to base snuffs out the oscillations.

(3) Notice that the oscillations are just microvolts, probably an artifact of the floating-point math, and whatever choice of termination criteria the approximation algorithm uses. It jut looks bad on the expanded scale graph that CircuitlLab chooses.