LTSpice transfer function

[Electronworks]

Anyone know how to do a transfer function in LTSpice?

Just as a quick circuit, I have connected a voltage ramp waveform to the base of an emitter follower. I want to plot the transfer function from base to emitter (then move on to move complex circuits later).

I have probed the base and the collector and have got transient analysis working quite happily. I cannot get the transfer function going though.

LTSPICE keeps spitting out the error: 'Transfer function source v not in circuit'.

Going back into the transfer function setup, I notice it has now changed my Vin reference to 'v'.

What am I doing wrong...?

All I want is a plot of Vin on the x axis and Vemitter on the Y axis.

 

[crutschow]

Post the circuit diagram of the simulation.

 

[Electronworks]

Here it is...

Let me know your comments...

Thanks!

 

[crutschow]

In some Spice simulators the Transfer Function is the S-plane Laplace transfer function, not the transient or DC transfer function. I suspect LTSpice may be the same.

If you are looking for a plot of input voltage versus output voltage, do a DC sweep (if LTSpice offers that function).

 

[MikeMl]

Look at the attached example

 

[Roff]

Here is an example. If you change the DC value of Vin, the transfer function will change.

 

[Electronworks]

Hi Mike and Ron

This is exactly what I am looking for. Thanks very much! I really appreciate it