Achieving optimum performance with a high-frequency amplifier like the OPA690 requires careful attention to board layout parasitics and external component types. Recommendations that optimize performance include:

1. Minimize parasitic capacitance to any ac ground for all of the signal I/O pins. Parasitic capacitance on the output and inverting input pins can cause instability: on the noninverting input, parasitic capacitance can react with the source impedance to cause unintentional band-limiting. To reduce unwanted capacitance, open a window around the signal I/O pins in all of the ground and power planes around those pins. Otherwise, ensure that the ground and power planes are unbroken elsewhere on the board.
2. Minimize the distance (< 0.25") from the power-supply pins to high-frequency 0.1-µF decoupling capacitors. At the device pins, ensure that the ground and power-plane layout is not in close proximity to the signal I/O pins. Avoid narrow power and ground traces to minimize inductance between the pins and the decoupling capacitors. Always decouple the power-supply connections with these capacitors. An optional supply decoupling capacitor (0.1-µF) across the two power supplies (for bipolar operation) improves 2nd-harmonic distortion performance. Also, use larger (2.2-µF to 6.8-µF) decoupling capacitors, effective at lower frequencies, on the main supply pins. Place these decoupling capacitors somewhat farther from the device and share these capacitors among several devices in the same area of the PCB.
3. Careful selection and placement of external components preserve the high-frequency performance of the OPA690. Use very low reactance type resistors. Surface-mount resistors work best and allow a tighter overall layout. Metal film or carbon composition axially-leaded resistors can also provide good high-frequency performance. Again, keep the leads and PCB traces as short as possible. Never use wire-wound type resistors in a high-frequency application. Because the output pin and inverting input pin are the most sensitive to parasitic capacitance, always position the feedback and series output resistor, if any, as close as possible to the output pin. Place other network components, such as noninverting input termination resistors, close to the package. Where double-side component mounting is allowed, place the feedback resistor directly under the package on the other side of the board between the output and inverting input pins. Even with a low parasitic capacitance shunting the external resistors, excessively high resistor values can create significant time constants that can degrade performance. Good axial metal film or surface-mount resistors have approximately 0.2 pF in shunt with the resistor. For resistor values > 1.5 kΩ, this parasitic capacitance can add a pole or zero below 500 MHz that can affect circuit operation. Keep resistor values as low as possible consistent with load driving considerations. The 402-Ω feedback is a good starting point for design. A 25-Ω feedback resistor, rather than a direct short, is suggested for the unity-gain follower application. This configuration effectively isolates the inverting input capacitance from the output pin that can otherwise cause an additional peaking in the gain of 1 frequency response.
4. Connections to other wideband devices on the board can be made with short, direct traces or through onboard transmission lines. For short connections, consider the trace and the input to the next device as a lumped capacitive load. Use relatively wide traces (50 mils or 1.27 mm to 100 mils or 2.54 mm), preferably with ground and power planes opened up around the traces. Estimate the total capacitive load and set R_S from the plot of Recommended R_S vs Capacitive Load (Figure 6-51 for ±5 V and Figure 6-66 for 5 V). Low parasitic capacitive loads (< 5 pF) do not always require an R_S because the OPA690 is nominally compensated to operate with a 2-pF parasitic load. Higher parasitic capacitive loads without an R_S are allowed as the signal gain increases (increasing the unloaded phase margin). If a long trace is required, and the 6-dB signal loss intrinsic to a doubly-terminated transmission line is acceptable, implement a matched impedance transmission line using microstrip or stripline techniques (consult an ECL design handbook for microstrip and stripline layout techniques). A 50-Ω environment is normally not necessary on board, and in fact, a higher impedance environment improves distortion (see also the distortion versus load plots). With a characteristic board trace impedance defined (based on board material and trace dimensions), a matching series resistor into the trace from the output of the OPA690 is used, as well as a terminating shunt resistor at the input of the destination device. Remember also that the terminating impedance is the parallel combination of the shunt resistor and the input impedance of the destination device; set this total effective impedance to match the trace impedance. The high output voltage and current capability of the OPA690 allows multiple destination devices to be handled as separate transmission lines, each with series and shunt terminations. If the 6-dB attenuation of a doubly-terminated transmission line is unacceptable, a long trace can be series-terminated at the source end only. Treat the trace as a capacitive load in this case and set the series resistor value (see also the Recommended R_S vs Capacitive Load plot (Figure 6-51 for ±5 V and Figure 6-66 for 5 V). This configuration does not preserve signal integrity as well as a doubly-terminated line. If the input impedance of the destination device is low, there is some signal attenuation due to the voltage divider formed by the series output into the terminating impedance.
5. Socketing a high-speed part like the OPA690 is not recommended. The additional lead length and pin-to-pin capacitance introduced by the socket can create an extremely troublesome parasitic network that can make achieving a smooth, stable frequency response almost impossible. Best results are obtained by soldering the OPA690 onto the board.