7.3.3 Driving Capacitive Loads

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.

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, RISO, in series with the output. This resistor

significantly reduces the overshoot and ringing associated with capacitive loads.

R

ISO

IN+

R

ISO

IN+

R

F

R

G

Gain = 1 V/V

Gain

1 V/V

TLV365

TLV365

Figure 7-4. Improving Capacitive Load Drive

A possible drawback of this technique is the voltage divider created with the added series resistor (RISO) and

any resistor (RL) 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 RL = 10 kΩ and RISO = 20 Ω, the gain error is only approximately 0.2%.

The following figure shows the recommended isolation resistor (RISO) 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 7-5. Recommended Isolation Resistor vs Capacitive Load

TLV365, TLV2365

SBOSAA8C – DECEMBER 2022 – REVISED AUGUST 2024

www.ti.com

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