probe_ac :
An AC analysis probe for measuring frequency-domain, AC transfer function.

The probe_ac primitive measures the frequency-domain transfer function of a circuit by supplying an AC stimulus (stim) and measuring the circuit’s response (resp). That is, one can measure a frequency-domain transfer function by configuring a testbench that feeds the stim output of this primitive to the circuit’s input and connects the circuit’s output to the resp input of this primitive.

The stimulus stim is a sinusoidal chirp signal with specified DC offset (stim_dc) and AC amplitude (stim_ac), and with frequency varying from freq_start to freq_stop over the time period after an initial delay delay. Over the course of simulation, the probe_ac primitive measures the response at each frequency value and records the corresponding transfer function magnitude and phase values in a table format to a text file named by the parameter filename. The simulation must be run longer than delay+period in order for the primitive to collect the entire transfer function.

Input/Output Terminals

Name	I/O	Type	Description
stim	output	xreal	stimulus (to circuit)
resp	input	xreal	response (from circuit)

Parameters

Name	Type	Default	Unit	Description
filename	string	“probe_ac.dat”	None	output filename
stim_dc	real	0.0	None	stimulus DC offset
stim_ac	real	1.0	None	stimulus AC amplitude
freq_start	real	10.0e6	Hz	start frequency
freq_stop	real	10.0e9	Hz	stop frequency
period	real	1e-6	seconds	sweep period
delay	real	0.0	seconds	initial delay