What is the flow to design a, let's suppose 2 bit Sigma delta modulator? Would Xschem be all i would need or is there a particular set of applications, since the design is mixed signal in nature.

The design flow I'm using: • Design circuit: Xschem + ngspice. Simulate until requirements are fulfilled using TT models. • Verify for all process corners, voltages, device mismatch, temerpatures: Xschem, ngspice, home-made python scripts. • Layout + LVS + DRC: Magic and netgen • Post layout simulation: Again all process corners etc. (see above) All in all it's a lot of work. I'm currently implementing a precision current source and a low noise / high bandwidth TIA and it takes monthes to get good results.

Thank you Simon for sharing your workflow with me, it will definitely help me a lot! Also all the best to you, I hope you are able to complete your designs and send it off for tapeout.