Analog layout refers to the process of creating the physical layout of analog circuits, such as operational amplifiers, analog-to-digital converters, and filters. Analog circuits are used in a wide range of applications, including telecommunications, instrumentation, and consumer electronics
Analog layout differs from digital layout in several key ways. For example, analog circuits typically require more complex layouts, as they often have more components and interconnects than digital circuits. Analog circuits also require more careful attention to layout details, as even small variations in the placement of components and interconnects can have a significant impact on performance
The analog layout process involves several steps, including:
- Circuit design: This is the first step in the analog layout process, and it involves creating a schematic of the analog circuit
- Floorplanning: This step involves creating a high-level layout of the analog circuit, including the placement of major blocks and the allocation of space for different components.
- Placement: In this step, the individual components are placed on the silicon wafer. This step is critical for ensuring that the circuit meets performance and power constraints, as well as for minimizing the total area used by the circuit
- Routing: In this step, the interconnects between the components are created. This step is critical for ensuring that the circuit meets performance and power constraints, as well as for minimizing the total area used by the circuit.
- Parasitic extraction: In this step, the parasitic elements, such as resistance and capacitance, are extracted from the physical layout and incorporated into the simulation models used in verification.
- Layout versus schematic (LVS) verification: In this step, the physical layout is compared to the original design to ensure that it meets the specifications and requirements.
- Design rule checking (DRC): In this step, the physical layout is checked against a set of design rules to ensure that it meets the fabrication requirements.
Analog layout requires a strong understanding of analog circuit design, as well as expertise in areas such as computer-aided design (CAD) and optimization algorithms. Analog designers use specialized tools, such as physical design automation (PDA) software, to aid in the creation of the physical layout.