Single/Dual/Quad, Low-Power, Single-Supply,

Rail-to-Rail I/O Op Amps with Shutdown

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11

Rail-to-Rail Output Stage

The MAX4330–MAX4334 output stage can drive up to a

2k

Ω load and still typically swing within 125mV of the

rails. Figure 3 shows the output voltage swing of a

MAX4331 configured as a unity-gain buffer. The operat-

ing voltage is a single +3V supply, and the input volt-

applied (2k

Ω to mid-supply).

Driving a capacitive load can cause instability in many

op amps, especially those with low quiescent current.

The MAX4330–MAX4334 are stable for capacitive loads

up to 150pF. The Capacitive Load Stability graph in the

Typical Operating Characteristics gives the stable

operating region for capacitive vs. resistive loads.

Figures 4 and 5 show the response of the MAX4331

with an excessive capacitive load, compared with the

response when a series resistor is added between the

output and the capacitive load. The resistor improves

the circuit’s response by isolating the load capacitance

from the op amp’s output (Figure 6).

1k

1k

Figure 2. Input Protection Circuit

Figure 3. Rail-to-Rail Input/Output Voltage Range

IN

1V/div

1V/div

OUT

20

µs/div

Figure 4. Small-Signal Transient Response with Excessive

Capacitive Load

IN

50mV/div

50mV/div

OUT

2

µs/div