Amplifiers driving capacitive loads can oscillate or have ringing at the output. To eliminate oscillation or reduce ringing, place an isolation resistor as shown in Figure 6-9. The combination of the isolation resistor and the load capacitor forms a pole to increase stability by adding more phase margin to the overall system. The desired performance depends on the value of the isolation resistor; the bigger the isolation resistor, the more damped the pulse response becomes. For LM7171, a 50Ω isolation resistor is recommended for initial evaluation. Figure 6-10 shows the LM7171 driving a 150pF load with the 50Ω isolation resistor.

Figure 6-9 Isolation Resistor Used to Drive Capacitive Load

Figure 6-10 The LM7171 Driving a 150pF Load With a 50Ω Isolation Resistor