When using high-speed operational amplifiers, it is extremely important to consider the effects of capacitive loading on amplifier stability. Capacitive loading will interact with the output impedance of the operational amplifier, and depending on the capacitor value, can significantly decrease the gain bandwidth, as well as introduce peaking. To reduce the effects of capacitive loading and allow for additional capacitive load drive, place a series resistor between the output and the load. This will reduce available bandwidth, but permit stable operation with capacitive loading. Figure 7-1 illustrates the recommended relationship between the resistor and capacitor values.

Amplifiers configured in unity gain are most susceptible to stability issues. The typical characteristic, Figure 5-16 describes the relationship between capacitive load and stability for the OPA300/OPA301 series. In unity gain, the OPA300/OPA301 series is capable of driving a few picofarads of capacitive load without compromising stability. Board level parasitic capacitance can often fall into the range of a picofarad or more, and must be minimized through good circuit-board layout practices to avoid compromising the stability of the OPA300/OPA301. For more information on detecting parasitics during testing, see the Application Note Measuring Board Parasitics in High-Speed Analog Design , available at the TI web site www.ti.com.