determine the gain of an amplifier

Not with only that information. If you also have the circuit, it may be possible, depending on the accuracy you want and the details of the circuit.

Cheers, Tom

So, I have the bias point (0.75V) and the 1 mV input signal voltage added to the bias point (0.75+0.001)= 0.751V

Then doesn't Vout/Vin = gain?

Or am I complete wrong on this ?

Thanks

If you are amplifying a DC signal, yes. Otherwise, the component models used for determining the DC operating point of an amplifier (treating capacitors as open circuit, for example) don't give you the correct answer for an AC signal.

... Ah, OK, I didn't understand your original posting...I didn't realize that you had run (or proposed to run) the DC operating point for two values of input. In that case, the DC gain between two points (the input and output) should be clear, as you suggest. That doesn't apply at other frequencies, however, and will in general change if you put a load on the amplifier. It also assumes linearity; if the gain is high, that may not be valid.

analysis. Why not run a .AC or .TRAN analysis? The .AC will easily give you gain as a function of frequency, assuming linearity about the determined DC operating point, and the .TRAN can give you gain at discrete frequencies, and show nonlinearities as well.

Cheers, Tom