The OPA698 is internally compensated to be unity-gain stable, and has a nominal phase margin of 60° at a gain of 2V/V. Phase margin and peaking improve at higher gains. Recall that an inverting gain of –1V/V is equivalent to a gain of 2V/V for bandwidth purposes (that is, noise gain = 2V/V). Standard external compensation techniques work with this device. For example, in the inverting configuration, the bandwidth is limited without modifying the inverting gain by placing a series RC network to ground on the inverting node. This configuration has the effect of increasing the noise gain at high frequencies, which limits the bandwidth.

To maintain a wide bandwidth at high gains, cascade several op amps, or use the high-gain optimized OPA699.

In applications where a large feedback resistor is required, such as a photodiode transimpedance amplifier, the parasitic capacitance from the inverting input to ground causes peaking or oscillations. To compensate for this effect, connect a small capacitor in parallel with the feedback resistor. The bandwidth is limited by the pole that the feedback resistor and this capacitor create. In other high-gain applications, use a three-resistor Tee network to reduce the RC time constants set by the parasitic capacitances. Be careful not to increase the noise generated by this feedback network too much.