** Next:** .tran Line
** Up:** Analysis Specification
** Previous:** .sens Line
** Contents**
** Index**

##

`.tf` Line

- General Form:

`.tf `*outsrc* | v(*n1*[,*n2*]) `insrc`
[ac dec|oct|lin *np fstart fstop*]
[dc|
sweep *args*]

- Examples:

`.tf v(5,3) vin
`

.tf I(vload) vin ac dec 10 1 1e12

.tf v(2) vin ac dec 10 1 1meg

.tf v(4) vx dc vcc 5 10 1

.tf v(5) vy ac dec 10 1 1meg dc 5 10 1

The `.tf` line defines the small-signal output and input for the
dc or ac small-signal analysis. The first parameter is the
small-signal output variable (node voltage or name of inductor or
voltage source for branch current) and *insrc* is the small
signal input source. If this line is included, *WRspice* computes
the dc or ac small-signal value of the transfer function
(output/input), input resistance or impedance, and output resistance
or impedance. For the first example, *WRspice* would compute the
ratio of `v(5,3)` to `vin`, the small signal input resistance
at `vin`, and the small-signal output resistance measured across
nodes 5 and 3. If the ac parameters are given, the `.tf` line
produces output vectors representing the impedance and other
parameters at each frequency point.

The optional dc sweep is a dc analysis specification which will cause
the transfer function analysis to be performed at each point of the dc
sweep. The small-signal parameters are reevaluated at every sweep
point, and the output vectors will be multidimensional.

In interactive mode, the **tf** command, which takes the same
arguments as the `.tf` line, can be used to initiate transfer
function analysis.

Transfer function analysis is not available if Josephson junctions are
included in the circuit.

** Next:** .tran Line
** Up:** Analysis Specification
** Previous:** .sens Line
** Contents**
** Index**
Stephen R. Whiteley
2021-01-27