Chapter 17 - Circuit Board Layout Techniques

Abstract

Op amp circuitry is analog circuitry, and is very different from digital circuitry. It must be partitioned in its own section of the board, using special layout techniques. Printed circuit board (PCB) effects become most apparent in high-speed analog circuits, but common mistakes described in this chapter can even affect the performance of audio circuits. This chapter discusses some of the more common mistakes made by designers and how they degrade performance, and provide simple fixes to avoid the problems. In all but very rare cases, the PCB layout for analog circuitry must be designed such that the effect of the PCB is transparent to the circuit. Any effect caused by the PCB itself should be minimized, so that the operation of the analog circuitry in production will be the same as the performance of the design and prototype. For circuit board layouts, a designer should use a high-quality board material such as FR-4; multi-layer boards are as much as 20-dB better than double-sided boards. Also, one should use separate, nonoverlapping ground and power planes and should place power and ground planes to the interior of the board instead of exterior.