Large-Signal Transfer Function

[ngox]

Is there some way to obtain a 'large-signal transfer function' for an amplifier? I'm designing a broadband amplifier and when I look at the transient waveform, there is a significant amount of overshoot and ringing, yet the small-signal analysis results in a monotonic low-pass transfer function. To obtain the large-signal performance, thus far I've just been running transient sim with sine wave input of different frequencies and looking at the output amplitude... which is a rather tedious process. Are there any built in tools in Cadence Virtuoso that can do this automatically?

 

[FvM]

By nature of "large signal" response, you get potentially different behavior for different signal waveform and magnitude. Therefore it's usual to test large signal behavior with waveforms similar to the actual amplifier application.

 

[LvW]

Large signal operation - in contrast to small-signal operation - is connected with distortions (deviations from the sinusoidal waveform).
That means: Input and output waveforms are different. Therefore, it is a bit "problematic" to define something like a "transfer function".
More than that, these distortions depend on the amplitudes of the "large signals".

 

[ngox]

Thanks for the responses. The input amplitude is relatively well defined, so I have been using that to prime the input in test bench.

 

[FvM]

That means: Input and output waveforms are different. Therefore, it is a bit "problematic" to define something like a "transfer function".

Agreed. A plausible definition would be gain of the fundamental wave, that's how RF power amplifiers are usually specified. You find large signal gain curves e.g. in OP datasheets as the below shown THS3001 specification, I assume the OP wants something similar.



I would do a simulation in a SPICE tool with parametric sweep and measurement functions.