How to set modulation depth with modulating a signal with an analog multiplier?
If V2 is a pure sinewave, and V1*V2=W, you aren't amplitude modulating the carrier, but DSBSC modulating it. As the "SC" in DSBSC means "Suppressed Carrier", there is no carrier energy, so the concept of "modulation depth", the ratio of signal amplitude to carrier amplitude, doesn't apply there.

The difference is that in DSBSC, the modulated output is 0 when V2=0 and inverted (180 degree phase "shifted") when V2 &lt; 0.

The secret to AM is to add a DC offset equal to V2 maximum amplitude, so that V2 never crosses 0. Instead, when V2 = -1 (the negative peak of the sinewave) it cancels out the DC offset and W = v1 * (V2+DC) = 0, for 100% modulation depth.

You can now reduce V2 gain keeping the DC offset unchanged, and modulation depth will reduce as desired.