Hi, Please make your project public, so we will follow. Modify the project and set it public. then tell us when it is ready. ![enter image description here][1] [1]: /editor/20150817/55d10c3c84c92.png

Hi Ankit, The ADA4899-1 has a thermal pad on the bottom of the package. To make the pinout work when mapping pins on the 8 pin device plus a thermal pad onto an 8 pin plus thermal pad footprint, the thermal pad needs to be given a pin number (9 in this case). You will need to create a suitable 9 pin footprint based on the 8 pin SOIC with a 9th pad of the right shape in the middle of the package. This is shown in Figures 3 and 5 of: >http://www.analog.com/media/en/technical-documentation/user-guides/UG-755.pdf It would seem that the thermal pad only has to be on the top (component side) layer and does not need to be connected to any other copper or layers by vias. We can comment more when you share your circuit. :)

There is now a working spice simulation and subckt for the ADA4988 available here: >http://easyeda.com/andyfierman/ADA4899_1_transimpedance_amplifier-bEaGYSM4m