Automotive, industrial, medical, and many other applications use sensitive analog circuits that must perform their function while remaining immune to noise disturbances in their local environment. Many of these disturbances occur on nearby “noisy” circuits located on the same printed circuit board (PCB), while other interference can be picked up by cable interfaces that couple noise onto the PCB and its circuits.
One of the best ways to reduce electromagnetic interference (EMI) on PCB designs is through intelligent use of operational amplifiers (op amps). Unfortunately, op amps are often overlooked as a tool for reducing EMI in many applications. This may be due to the perception that op amps are susceptible to EMI and that extra steps must be taken to enhance their immunity to noise. While this is true of many older devices, designers may not be aware that newer op amps often have superior immunity performance over previous generations. Designers also may not understand or consider the key benefits that an op amp circuit can provide for reducing noise in their system and PCB designs. This article reviews sources of EMI and discusses op amp characteristics that aid in mitigating near-field EMI on sensitive PCB designs.