I am trying to simulate an AD8099 cascaded amplifier (please see the attached). Each stage amplifies x10, and the overall gain should be x100.
First I built the circuit using the FB pins of AD8099 as in the attached circuit and did an AC analysis, but the obtained gains at each stage were x7.3 and x62.3, which are way smaller than (I believe) what they should be. Then I reconnected the feedback resistors to the Vout (gave up using FB pins) and finally got gains I expected.
This happens in both MultiSim and LTSpice (although the gains are different when using FB pins).
Is this the simulation only issue? Or does this happen even in a real circuit?
Thanks in advance!
The error that you encountered is most probably just a spice model issue and your circuit should be working fine. But I will still verify this on the application engineer of this part or try to replicate this on our lab to make sure that your circuit will not have any trouble.
I looked at the spice model, and it does have a problem. I have notified the product line.
In the meantime, just use the output pin. When you actually do your board, definitely
put the chip resistor between the FB pin and the inverting input.
Hi Emman and Harry,
Thank you very much! I'll use the output pin instead for now.
About the AD8099 spice model problem - are any updates from the product line folks? (the posted spice model is dated 2012). Or can you share on the nature of the problem?