I am designing an AGC feedback loop with an AD8331 vga. The spice model given on your website works with the transient analysis, but I have an issue with the .ac analysis.
When I put an AC source on the input pin, the simulation works fine, and I can for example plot the gain for different values of Vgain.
However, when I put an AC source on the gain pin (to observe the phase margin of my feedback loop), the output of the AD8331 stays at -390dB, no matter the conditions.
Is there a way to study the AGC loop stability with your model ?