AD588
Data Sheet
Attempts to drive a large capacitive load (in excess of 1000 pF)
can result in ringing or oscillation, as shown in the step response
photo (Figure 29). This is due to the additional pole formed by
the load capacitance and the output impedance of the amplifier,
which consumes phase margin.
V
IN
The recommended method of driving capacitive loads of this
magnitude is shown in Figure 30. The 150 Ω resistor isolates the
capacitive load from the output stage, while the 10 kΩ resistor
provides a dc feedback path and preserves the output accuracy.
The 1 µF capacitor provides a high frequency feedback loop.
The performance of this circuit is shown in Figure 31.
V
OUT
Figure 31. Output Amplifier Step Response Using Figure 30 Compensation
V
IN
V
OUT
Figure 29. Output Amplifier Step Response, CL = 1 µF
10kΩ
1µF
150Ω
V
OUT
C
1µF
L
+
V
IN
–
Figure 30. Compensation for Capacitive Loads
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