// Source-build example: one RC topology, two independent cutoff settings.
// Change fast_cutoff to change only FAST; the fixed assertions are not retuned.
// Formula assumes an ideal input source and no output load or component tolerance.
param slow_cutoff: Hz = 500Hz
param fast_cutoff: Hz = 2kHz
module LowPass(input,output,gnd) {
  param resistance: Ohm = 1k
  param cutoff: Hz = 1k
  param capacitance: F = 1 / (2 * pi * resistance * cutoff)
  resistor R1 {resistance}
  capacitor C1 {capacitance}
  connect input to R1.p1
  connect R1.p2, C1.p1 to output
  connect C1.p2 to gnd
}
net GND
net IN
net SLOW_OUT
net FAST_OUT
source VIN ac(1V)
use LowPass SLOW(cutoff={slow_cutoff})
use LowPass FAST(cutoff={fast_cutoff})
connect VIN.plus, SLOW.input, FAST.input to IN
connect VIN.minus, SLOW.gnd, FAST.gnd to GND
connect SLOW.output to SLOW_OUT
connect FAST.output to FAST_OUT
simulate ac dec 80 1Hz 100kHz
assert upper_cutoff(V(SLOW_OUT),V(IN)) > 495Hz
assert upper_cutoff(V(SLOW_OUT),V(IN)) < 505Hz
assert upper_cutoff(V(FAST_OUT),V(IN)) > 1980Hz
assert upper_cutoff(V(FAST_OUT),V(IN)) < 2020Hz