Single/Dual/Quad, Micropower,

Single-Supply Rail-to-Rail Op Amps

12

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in series with IN-, IN+, or both. Series resistors are not

recommended for amplifier applications, as they may

increase input offsets and decrease amplifier bandwidth.

Output Loading and Stability

Even with their low quiescent current of less than 150µA

per op amp, the MAX492/MAX494/MAX495 are well

suited for driving loads up to 1k

Ω while maintaining DC

accuracy. Stability while driving heavy capacitive loads

is another key advantage over comparable CMOS rail-

to-rail op amps.

In op amp circuits, driving large capacitive loads

increases the likelihood of oscillation. This is especially

true for circuits with high loop gains, such as a unity-

gain voltage follower. The output impedance and a

capacitive load form an RC network that adds a pole to

the loop response and induces phase lag. If the pole

frequency is low enough—as when driving a large

capacitive load—the circuit phase margin is degraded,

leading to either an under-damped pulse response or

oscillation.

10

µs/div

50mV/div

50mV/div

10

µs/div

50mV/div

50mV/div

10

µs/div

50mV/div

50mV/div

Figure 7c. MAX492 Voltage Follower with 500pF Load—

Figure 7a. MAX492 Voltage Follower with 500pF Load—

Figure 7b. MAX492 Voltage Follower with 500pF Load—

50mV/div

50mV/div

10

µs/div

Figure 6. MAX492 Voltage Follower with 1000pF Load