The TLVx365 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.

Figure 8-4 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 8-4 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%.

Figure 9-33 shows the recommended isolation resistor (R_ISO) to be connected at the output of TLVx365 for different capacitive loads. The TLVx365 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 8-5 Recommended Isolation Resistor vs Capacitive Load