I am trying to make this particular Wien Bridge Oscillator (WBO) circuit using LTspice. Ideally I should get an output sine signal. Although I can't seem to make it work. Anything wrong with what I did here? It only shows this straight line with no change in Amplitude.
2 Answers
A main issue you are having is understanding the potentiometers.
The arrow does not simply denote an arrow of some sort as a hint, it is an electrical contact which you have to model in your simulation as well.
You can think of a potentiometer as two resistors. The sum of the two resistor values is the value of the potentiometer, and the slider (arrow) will choose the value of the two single resistors. Like in this example:
simulate this circuit – Schematic created using CircuitLab
So I don't know of a component in LT Spice which handles this internally, so I model this manually. If you want to get fancy you could use formulas to recreate this behaviour.
If the potentiometer only has a two connections used, you can replace it with a single resistor as the other one would be dangling in the air (one side unconnected, which doesn't help the simulation)
Another mistake is the polarity of the opamp inputs, you have reversed them from the original schematic. You can mirror components horizontally if you don't want to mess with the wires, but then you have to change your supply rails accordingly (because those will be flipped as well).
If your circuit does not start to oscillate or behaves strange, it can sometimes help to select "startup voltages" (or something like that, my LT Spice doesn't open for some reason, sorry) in the transient simulation tab.
R1
is a simple resistor acrossC2
, so delete that arrow you've drawn and instead of ground at the end ofR1
make the connection acrossC2
. Then the values ofR1
and/orR3
can be changed, since they are potentiometers in the original schematic. Also, there's no need to.lib opamp.sub
since you've used real models (LT1001
). \$\endgroup\$