Can someone help with .noise analysis of my circuit?

Nano81 · June 28, 2025, 6:30am

I have a circuit that I would like to find out how much noise it will produce. THD and Phase is really nice, but when I try to do a .noise command, I’m not sure if I am using correct syntax.

Here is the qsch file
Baby Tiger.qsch (22.2 KB)

I tried this command → .noise V(out) V6 list 1K

It doesn’t plot anything. If I try to click on the output manually I get what seems like a really high noise figure 86nvs. Is 86nvs a high noise level for a small signal amplifier? I am used to seeing it expressed as decibels. Need help. thanks.

bordodynov · June 28, 2025, 8:29am

See

Nano81 · June 28, 2025, 10:56am

Thank you very much! Two questions.

What is the pink line in the middle?

Is 12uv rms considered too much noise for this small signal circuit?

bordodynov · June 28, 2025, 3:44pm

And you’re looking at the input noise. 12uV is already an amplified noise as well as a signal. And the middle line is an Gain. Pay attention to the right vertical axis.