*I think I've found the answer myself. Check out the question comments.*
Sorry for my bad English, I'm still learning it.
This week I started using ngspice. I've built some simple circuits to get used to its netlist syntax and CLI commands. One of those circuits I've tried is the band-pass filter circuit with the following netlist:
Band-Pass Filter Vin 1 0 DC 0 AC 1 C1 1 2 0.0001m L1 2 3 1 R1 3 0 100 .AC LIN 1000 0.1 1000 .end
The simulation runs without any errors, but there's something weird with the results:
In node #3 I get the correct result (Figure 1: Node 3: Voltage vs Frequency): peak of 1V RMS, the same magnitude of input AC source.
But there's something wrong with node #2: its voltage has a peak of 30V RMS, while my input AC source is limited to 1V RMS (Figure 2: Nodes 1, 2 and 3: Voltage vs Frequency).
Do you guys have any ideas of why this is happening? Do you see anything wrong with my netlist? I appreciate any ideas on the subject.