The OPA835 and OPA2835 devices drive up to a nominal capacitive load of 10 pF on the output with no special consideration. When driving capacitive loads greater than 10 pF, TI recommends using a small resistor (R_O) in series with the output as close to the device as possible. Without R_O, output capacitance interacts with the output impedance of the amplifier causing phase shift in the loop gain of the amplifier that will reduce the phase margin. This will cause peaking in the frequency response and overshoot and ringing in the pulse response. Interaction with other parasitic elements may lead to instability or oscillation. Inserting R_O will isolate the phase shift from the loop gain path and restore the phase margin; however R_O can limit the bandwidth slightly.

Figure 8-5 shows the test circuit and Figure 7-41 shows the recommended values of R_O versus capacitive loads, C_L. See Figure 7-40 for the frequency responses with various values.

Figure 8-5 R_O versus C_L Test Circuit