I'm new to electronics and I'm learning some circuits with op amps. Now I have been shown this astable multivibrator.
I understand how it works.
- The op amp is saturated at one side or the other
- Voltage is divided and a portion of it goes to non-inverting input.
- Voltage also charges the capacitor until it gets equal to the voltage on the non-inverting output
- At that point the op amp swaps its output to the other saturation point.
Why is the op amp saturated at point 1 to begin with?
If I remove the capacitor (either shorting it, opening it or replacing it with a resistance), the op amp will sit at zero volts, since both inputs are zero, and that is totally what I would expect.
Why, by plugging in an uncharged capacitor, does the op amp suddenly decides to saturate?
The uncharged capacitor should not create any change in the difference of voltage between inverting and non inverting inputs that the op amp could amplify, so I would expect that in a perfect simulation this circuit would not start oscillating in the first place unless the capacitor does hold a tiny bit of charge.
Why does it start oscillating?
EDIT: so it turns out that in the simulator the capacitor actually had an initial voltage, and indeed if I set it to zero then the simulation will not oscillate.