Generally you need to include some initial disturbance to get the oscillator going.

In LTSpice you can use the "startup" and ".ic" (initial condition) directives to create that disturbance.

Here is an example:

The "startup" directive tells LTSpice to start the DC supply at 0V.

The ".ic" (initial condition) directive sets the initial voltage at node 1 instead of the voltage found by performing the DC analysis.

Without these directives this simulation does not oscillate.

Update: The disturbance might not have to be very large. In this above example I've found the voltage in the ".ic" directive can be made as low as 0.0000001V (0.1uV). Going to 0.01uV doesn't work, though.

Generally you need to include some initial disturbance to get the oscillator going.

In LTSpice you can use the "startup" and ".ic" (initial condition) directives to create that disturbance.

Here is an example:

The "startup" directive tells LTSpice to start the DC supply at 0V.

The ".ic" (initial condition) directive sets the initial voltage at node 1 instead of the voltage found by performing the DC analysis.

Without these directives this simulation does not oscillate.

If ngspice does not support the "startup" directive, I would try replacing your DC supply with a step function.

Update: The disturbance might not have to be very large. In this above example I've found the voltage in the ".ic" directive can be made as low as 0.0000001V (0.1uV). Going to 0.01uV doesn't work, though.

Generally you need to include some initial disturbance to get the oscillator going.

In LTSpice you can use the "startup" and ".ic" (initial condition) directives to create that disturbance.

Here is an example:

The "startup" directive tells LTSpice to start the DC supply at 0V.

The ".ic" (initial condition) directive sets the initial voltage at node 1 instead of the voltage found by performing the DC analysis.

Without these directives this simulation does not oscillate.

Generally you need to include some initial disturbance to get the oscillator going.

In LTSpice you can use the "startup" and ".ic" (initial condition) directives to create that disturbance.

Here is an example:

The "startup" directive tells LTSpice to start the DC supply at 0V.

The ".ic" (initial condition) directive sets the initial voltage at node 1 instead of the voltage found by performing the DC analysis.

Without these directives this simulation does not oscillate.

Update: The disturbance might not have to be very large. In this above example I've found the voltage in the ".ic" directive can be made as low as 0.0000001V (0.1uV). Going to 0.01uV doesn't work, though.