Another Example of Using Berkeley SPICE with nanoHUB
Example of an RLC circuit analysis:
Consider the circuit shown below:
In which the components have the following values:
0 V for t<0, 10 V for t> 0
to be determined
The goal is to determine the range of resistances that will produce
From the analysis of the resulting differential equation, the solutions
will oscillate if R2/(4L2) < 1/(LC). Thus, we
expect oscillations for cases when, for example, R = 100 Ω.
The SPICE simulation input file for the circuit that should oscillate is
which simulates the transient response of the circuit over the time interval
0 < t < 100 μs in time steps of 1 μs.
Clicking on Simulate produces the graph:
which indicates that the circuit oscillates with a frequency of 100kHz,
as expected based on f = (1/2π)(1/LC)1/2.
The minimum value of R for which the circuit is not expected to oscillate
is 590Ω. Simulating the same circuit but with R=600Ω gives
the following graph:
Again, remember that the convention used in SPICE is that the current I(V1)
is the current flowing into voltage source V1 and is therefore
negative when V1 makes the transition to a positive voltage.