Dear all,

I have the gain @100Khz in bode plot almost=1dB, while the actual gain= 20 log(Vout/Vin)=20 log(3/0.005)= 55.56dB (from the transient values)

Could someone please explain why I have this weird bode plot gain reading?

Regards

 

I think it is because the bode plot is expecting an input of 1 volt so the scale is wrong. I didn't draw it up and try it but I think that's it.

 

I think it is because the bode plot is expecting an input of 1 volt so the scale is wrong. I didn't draw it up and try it but I think that's it.

Could you tell me please what is the 1V that are you talking about?

 

I think the problem might be related to having a resistor whose value is dependent on the signal. I think the AC analysis linearizes things and so I don't know how it would deal with a voltage-dependent resistance.

 

Alshatri, when you like to see the gain (Vout/Vin) you must display the ratio Vout/Vin.
However, your Bode plot shows only Vout.
Only in case your AC input is 1Volt it is sufficient to display Vout (because it is identical to the gain).
Remark: I cannot see which resistor value is "dependent on the signal".

EDIT: Sorry, a sharper look on the drawing has revealed that R3 depends on the input.