When receiving low-level signals, limiting the bandwidth of the incoming signals into the system is often required. To limit bandwidth, place an RC filter at the noninverting terminal of the amplifier (see Figure 51).
If even more attenuation is required, a multiple pole filter is required. Use a Sallen-Key filter for this task; see Figure 52. For best results, the amplifier must have a bandwidth that is eight to ten times the filter frequency bandwidth. Failure to do this can result in phase shift of the amplifier.