7 Key Changes, Analog Designers Will Need to Make

1. Do not Mix Devices Having Different Dimensions

To make the chip modular, the analog designers should agree a limited set of transistor widths and lengths to use for all the circuits. To maximise RF performance, these ‘unit’ devices generally implement short channel lengths; whenever longer geometries are required (e.g. in opamps/mirrors), variations on this set of geometries shall be generated via series combinations.

This approach reduces the freedom of analog designers, but makes the layout more compact. In fact, FinFET rules discourage the mixing of devices with different W/L and the layout engineer ends up grouping in a single area all the devices having the same dimensions. Different devices cannot be placed in close proximity, and the long interconnects are likely to introduce parasitics that will limit performance.

1. 7 Key Changes, Analog Designers Will Need to Make
2. 1. Do not Mix Devices Having Different Dimensions
3. 2. Use Repeatable Patterns
4. 3. Estimate Interconnect Parasitics From the Start
5. 4. Use Digital Calibration to Correct Analog Errors
6. 5. Current Density limits the Transmitter Output Power
7. 6. High Flicker Noise Corner Frequency
8. 7. Simulations Are Slow