# how to understand "ac phase"

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#### liucheng311

##### Junior Member level 3
hi,dear all
how to understand the parameter "ac phase" in VSIN in analoglib;i use it in the simulation for small signal analysis, should i assign "ac phase" 0 or 180??
could anyone help me?

##### Full Member level 3
assign 0 to phase and 1 to amplitude to have the transfer function at the output. if you give an AC phase different than 0, you will observe the transfer function shifted by that phase.

liucheng311

### liucheng311

Points: 2

#### liucheng311

##### Junior Member level 3
i have another question:when i simulate the multiplying factor K in the equation VOUT=K*V1*V2(V1 and V2 are two terminals of the multiplier),i assign "ac phase" of one VSIN 0,the other 180.
what is wrong with this assigning??

##### Full Member level 3
provide more details. kind of simulation, circuit and so on

#### enjunear

i have another question:when i simulate the multiplying factor K in the equation VOUT=K*V1*V2(V1 and V2 are two terminals of the multiplier),i assign "ac phase" of one VSIN 0,the other 180.
what is wrong with this assigning??

At first look, it sounds like you are trying to use the multiplier as a signal combiner (mixer). If one signal is injected with a phase angle of 0 degrees, and the other is injected with a phase angle of 180 degrees, then your two signals cancel each other out. A*cos(θ+0) + A*cos(θ+180)... if θ=0, 360, etc, then A*cos(0) + A*cos(180) = A + (-A) = 0

If that's the case, try injecting on at 0 deg, and the other at 90 degrees. Then you should get a flat (DC) output signal vs. time.
A*cos(θ+0) + A*cos(θ+90) = A

liucheng311

Points: 2