Gilbert multiplier ac analysis

Hello,

I am trying to plot the ac response of a gilbert cell multiplier. I have set the differential pair inputs as V1 + v1 and V1 - v1. For the quad transistors, I have given V2 + v2 and V2 - v2 as inputs. To perform ac analysis, I have set the quad pairs ac magnitude as 0 and the diff pairs ac magnitude as 1, now after performing the simulation, I get some weird results for the ac output response :sad:, but I am able to get an amplified version of the input at the output when I perform the transient simulation.
Is it the right way to do the ac analysis for a gilbert cell multiplier?

Also, could you please let me know, if the quad transistors should be biased to work in the saturation region? I have read in the books stating that the quad transistors work as switch, so is it necessary to bias them(quad inputs) to work in the saturation region?

Please help !!!

The multiplier implements y = x*y and you set x or y to zero, what do you expect?

If AC analysis should make sense at all, you have to set the other input to a constant DC level.

FvM said:

The multiplier implements y = x*y and you set x or y to zero, what do you expect?

If AC analysis should make sense at all, you have to set the other input to a constant DC level.

Click to expand...

..... because the ac analysis is a linear one.