9.3.4 Slew Rate and Output Stage

In addition to wide bandwidth, the OPA858 features a high slew rate of 2000 V/µs . The slew rate is a critical parameter in high-speed pulse applications with narrow sub 10-ns pulses such as Optical Time-Domain Reflectometry (OTDR) and LIDAR. The high slew rate of the OPA858 implies that the device accurately reproduces a 2-V, sub-ns pulse edge as seen in Figure 20. The wide bandwidth and slew rate of the OPA858 make it an ideal amplifier for high-speed, signal-chain front ends.

Figure 52 shows the open-loop output impedance of the OPA858 as a function of frequency. To achieve high slew rates and low output impedance across frequency, the output swing of the OPA858 is limited to approximately 3 V. The OPA858 is typically used in conjunction with high-speed pipeline ADCs and flash ADCs that have limited input ranges. Therefore, the OPA858 output swing range coupled with the class-leading voltage noise specification maximizes the overall dynamic range of the signal chain.

Figure 52. Open-Loop Output Impedance (Z_OL) vs Frequency