CHAPTER 3 – Placement and Routing Considerations for Various Circuit Designs

This chapter provides an overview of placement and routing consideration for various circuit designs. A general-purpose analog circuit board is defined as one that uses common analog circuitry that operates at only a few megahertz (MHz) of bandwidth. This type of circuit is fairly forgiving of circuit board placement and routing oversights, but there are a few guidelines still to be followed. High-performance analog circuit boards contain analog circuitry that is either higher in bandwidth, higher in gain, lower in noise, or have larger dynamic range than a general-purpose analog circuit board. The active devices on a high-performance board tend to have both more gain and operate at higher frequencies. A ground ring is used to isolate a section of circuitry from the rest of the board. It is most useful for high-end op amps. Another important routing technique involves differential signals. These signals are often used to improve a system's dynamic range and noise immunity. A differential analog signal is actually a pair of signal lines with opposite DC values. In a typical differential signal application, a pair of differential signal lines is used to move a signal from a driver to a receiver.