Hi Guys,

I have a very simple oscillator circuit working on the bench:

• Vcc is 5V, V+ is 2.5V.
• This circuit operates at around 16MHz and produces a 0V biased sine-wave at the electrode.
• On the right hand side of C1, the sine wave is biased around 2.5V.
• The amplitude of the sine wave lessens, as the loading of the electrode to ground increases.
• R2 feeds into a detection circuit to measure the amplitude of the waveform off to the right hand side of the schematic.
• This circuit continues to oscillate after I remove C1 and R2.

As you can see, it's very simple. But frustratingly, I cannot seem to get it to simulate properly (I'm using NI Multisim). I've simplified it down and produced the simulated circuit:



Does anyone have any clues to help with getting this simulated circuit running? I feel I'm missing something quite fundamental.

Thanks,

Dan

 

In your simulated circuit there can be no current in the inductor and so no resonance.
In the 'real' circuit there will be stray capacitance on the non-inverting input and the actual input characteristics of the a 'real' op-amp.
Try the simulation with a real op-amp and/or with a small capacitance to ground from the non-inverting input.

 

You need C1=1nF in order to create a resonant LC. Also, set IC condition for C1, otherwise it will not run

 

I think the simplest op amp oscillator is the phase shift oscillator. It got resistors and capacitors, all resistors are the same, all capacitors are the same.

You got: resistors, capacitors and an inductor. I don't call that simple.