Rainbow Electronics MAX495 - Manual (Page 12)

MAX492/MAX494/MAX495
Single/Dual/Quad, Micropower,
Single-Supply Rail-to-Rail Op Amps
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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 µ s/div
V
IN
50mV/div
V OUT
50mV/div
10 µ s/div
V IN
50mV/div
V OUT
50mV/div
10 µ s/div
V
IN
50mV/div
V
OUT
50mV/div
Figure 7c. MAX492 Voltage Follower with 500pF Load—
R
L = ∞
Figure 7a. MAX492 Voltage Follower with 500pF Load—
R
L = 5k Ω
Figure 7b. MAX492 Voltage Follower with 500pF Load—
R
L = 20k Ω
V IN
50mV/div
V OUT
50mV/div
10 µ s/div
Figure 6. MAX492 Voltage Follower with 1000pF Load
(R
L =
∞
)