This document describes a technique using active feedback to minimize phase error in amplifier circuitry, thereby extending the effective bandwidth by more than an order of magnitude. The method is presented as a cost-effective alternative to using wideband amplifiers or cascading multiple stages, offering better performance than standard RC compensation which suffers from temperature drift.
The note details the theoretical basis for the technique, providing equations for magnitude and phase error, and compares the performance of single-stage, cascaded, and second-order compensation designs. It includes a practical example circuit using the OP-470 quad op amp to demonstrate the significant improvement in phase flatness and bandwidth.
| Unity-gain bandwidth of example op amp | 6MHz |
|---|---|
| Match requirement for op amps | 1 to 2% |
| Example circuit gain | 10 |
The wideband amplifier's greater expense is the main drawback to this approach.
While it increases bandwidth, it pays for this improvement with increasingly higher costs and noise levels.