The TLVx365-Q1 can be used in applications where driving a capacitive load is required. An op amp in a unity-gain, buffer configuration and driving a capacitive load exhibits a greater tendency to be unstable than an amplifier operated at a higher gain. The capacitive load, in conjunction with the op-amp output impedance, creates a pole within the feedback loop that degrades the phase margin. The degradation of the phase margin increases as the capacitive loading increases. This degradation is observed in the increase in peaking with increased capacitive load in Figure 6-16.

Improving Capacitive Load Drive shows one technique to increase the capacitive-load drive capability of the amplifier operating in unity gain is to insert a small resistor, R_ISO, in series with the output. This resistor significantly reduces the overshoot and ringing associated with capacitive loads.

Figure 7-4 Improving Capacitive Load Drive

A possible drawback of this technique is the voltage divider created with the added series resistor (R_ISO) and any resistor (R_L) connected in parallel with the capacitive load. The voltage divider introduces a gain error at the output that also reduces the output swing. The error contributed by the voltage divider can be insignificant. For instance, with a load resistance of R_L = 10 kΩ and R_ISO = 20 Ω, the gain error is only approximately 0.2%.

The following figure shows the recommended isolation resistor (R_ISO) to be connected at the output of TLVx365-Q1 for different capacitive loads. The TLVx365-Q1 can drive higher capacitive loads without the need of isolation resistors at higher gains.

For gain > 1 V/V, RF = 1 kΩ

For gain = 1 V/V, RF = 0 Ω

Figure 7-5 Recommended Isolation Resistor vs Capacitive Load