im into amplifing biosignals too, im simulating with ac

[electro david]

im into amplifing biosignals too, im simulating with ac waveforms ( one with 12 mv peak, the other with 10 mv peak) with two generators and i calculated a Gain of 1000 but i got 2000 instead 1000, furthermore i have not offset, any idea why of this?

 

[godfreyl]

There is probably a mistake in your circuit or in your calculation.
If you want somebody to help you find the problem, you need to show a picture of the circuit.

 

[electro david]

Here is a picture of the circuit. RG for AD620= 49,400/G-1 = 49,400/999 = 49.45 ohms

 

[godfreyl]

That's odd. Your calculation looks correct and your circuit looks fine. Maybe the spice model used by your simulator is wrong?

As an experiment, I would try setting Rg to 49.4K (should give a gain of two), and try removing Rg (should give unity gain).

If you think the apice model's wrong, you could try downloading and installing the one here: **broken link removed**