AM modulation

[f2t1]

hi..anyone pls help me with this. have uploaded my am modulation circuit.but quite confused on how to calculate the percent of modulation.The lab manual i am referring states that m = Vmax-Vmin/Vmax + Vmin = Vm/Vc.

i set the Vm = 100mVp,Vc=0.75Vp so i must get m=0.13
however i did not get the same modulation index from the simulation circuit.
this is what i get Vmax=105mVp,Vmin=5mVp so m=0.91

 

[audioguru]

A 741 opamp is 43 years old. It has trouble with frequencies above 9kHz but you are trying to feed it 159kHz.
Maybe your sim program doesn't know it won't work.

 

[Dragon Tamer]

In Multisim, try using an LMV851MG, it has a much better frequency response than the 741.