Hi, I want to run a operating point analysis in ngspice and extract voltage values at specific nodes, and then use these values as initial conditions on capacitor attached to the same nodes in the transient analysis, can I do this.

Normally if you start a

.tran

analysis without the

uic

ending parameter the initial point is the solution of the

.OP

analysis. Ensure the time 0 transient value of all voltage / current sources matches the value used for OP analysis. This means do not set a voltage source like this:

va node a 0 dc 3 pwl 0 0 10n 0 11n 1.8

this voltage source will 3V for

op

analysis and starts at 0 in

tran

analysis.