.TF inner_sweep_spec [ V ] pos_out_node [ VN ] neg_out_node
+ [[ INSRC ] in_source ] [ F frequency ] [RUNNAME=runname]
[SWEEP outer_sweep_spec ]
.TF inner_sweep_spec  I  source  [ INSRC in_source ]
+ [ F frequency ] [RUNNAME=runname] [SWEEP outer_sweep_spec ]
Spice Compatible:
.TF V( pos_out_node [, neg_out_node ]) in_source
.TF I (source)  [ INSRC ] in_source

This statement instructs the simulator to perform a small signal transfer function analysis.

pos_out_node Output node.
neg_out_node Output reference node. Defaults to ground if omitted for standard SPICE syntax.
in_source Name of input source to which input noise will be referred.
inner_sweep_spec See General Sweep Specification for syntax. Defines sweep mode.
outer_sweep_spec If specified, analysis will be repeated according to this specification. See General Sweep Specification for syntax.
frequency Frequency at which analysis will be performed for non-frequency sweeps. Default 0.
source Voltage source to specify output current.
runname If specified, the value for runname will be passed to the simulation data group as a string variable with name UserRunName. This may be used to identify which analysis generated the data which is useful when running netlists with multiple analyses defined

In this topic:


The SIMetrix transfer function analysis remains syntax compatible with the SPICE version but is substantially enhanced. The SPICE version performs the analysis at a single point with frequency = 0. The SIMetrix implementation performs a swept analysis using the same sweep algorithm used for AC, DC and NOISE.

Transfer function analysis is similar to AC analysis in that it performs a swept small signal analysis. However, whereas AC analysis calculates the response at any circuit node from a (usually) single input source, transfer function analysis calculates the individual responses from each source in the circuit to a single specified output node. This allows, for example, the series mode gain, common mode gain and power supply rejection of an amplifier to be measured in one analysis. The same measurements could be performed using AC analysis but several of them would need to be run. Transfer function mode also calculates output impedance or admittance and, if an input source is specified, input impedance.

The names of the output vectors will be of the form
Input voltage, output voltage
Input voltage, output current
Input current, output voltage
Input current, output current

Output impedance for voltage out will be called Zout. For a current output, the output admittance will be calculated and will be named Yout.

If an input source is specified the input impedance will be calculated and called Zin.

Note that although the syntax for .TF retains compatibility with SPICE and earlier versions of SIMetrix, the output provided is slightly different. Firstly, the data is complex even if F=0 and secondly the names of the output vectors are different as detailed above.


SPICE compatible. Outputs results at DC.

.TF V(Vout) Vin

As above but decade sweep from 1k to 100k

.TF FREQ DEC 25 1K 100K V(Vout, 0) Vin

Note that in the above example the '0' in V(Vout, 0) is compulsory. If is omitted, Vin will be assumed as the reference node.