LAPLACE
Currently ngspice does not offer a direct E-Source element with the LAPLACE option. There is however a XSPICE code model equivalent called s_xfer (see Chapt. 12.2.16), which you may invoke manually. The XSPICE option has to be enabled (32.1). AC (15.3.1) and transient analysis (15.3.9) is supported.
The following E-Source:
ELOPASS 4 0 LAPLACE {V(1)}
+ {5 * (s/100 + 1) / (s^2/42000 + s/60 + 1)}
may be replaced by:
AELOPASS 1 int_4 filter1
.model filter1 s_xfer(gain=5
+ num_coeff=[{1/100} 1]
+ den_coeff=[{1/42000} {1/60} 1]
+ int_ic=[0 0])
ELOPASS 4 0 int_4 0 1
where you have the voltage of node 1 as input, an intermediate output node int_4 and an E-source as buffer to keep the name `ELOPASS' available if further processing is required.
If the controlling expression is more complex than just a voltage node, you may add a B-Source (5.1) for evaluating the expression before entering the A-device.
E-Source with complex controlling expression:
ELOPASS 4 0 LAPLACE {V(1)*v(2)} {10 / (s/6800 + 1)}
may be replaced by:
BELOPASS int_1 0 V=V(1)*v(2)
AELOPASS int_1 int_4 filter1
.model filter1 s_xfer(gain=10
+ num_coeff=[1]
+ den_coeff=[{1/6800} 1]
+ int_ic=[0])
ELOPASS 4 0 int_4 0 1