Differences Between PCB & IC Design

  • IC design is at the transistor level. (digital ASIC's excepted)
  • PCBs stress low component count, chips stress small size.
  • IC signal processing is fully differential, PCB tends to be ground referenced.
  • ICs emphasize the matching of components (so-called "ratiometric" designs) while tolerating looser absolute values and poorer thermal characteristics. 
  • Parasitic devices, inherent to fabrication, are a primary issue in IC designs.
  • ESD and electromigration are a major issue in chips.
  • IC's avoid using large value resistors or capacitors due to area.

  • IC's eliminate resistors as much as possible using current mirrors and other circuit design techniques.
  • In chips, due to limited externally accessible circuit nodes, design-for-testability issues are much more demanding.
  • Due to IC fabrication cycles that take 1-3 months, and high fabrication costs, the "breadboard, measure and adjust" methodology is not viable. Chip design is done totally with SPICE-type simulation tools.


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