S in g le /Du a l/Qu a d , Mic ro p o w e r,
S in g le -S u p p ly Ra il-t o -Ra il Op Am p s
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.
In op a mp c irc uits , d riving la rg e c a p a c itive loa d s
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
fre q ue nc y is low e noug h—a s whe n d riving a la rg e
capacitive load—the circuit phase margin is degraded,
leading to either an under-damped pulse response or
oscillation.
Ou t p u t Lo a d in g a n d S t a b ilit y
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 1kΩ while maintaining DC
accuracy. Stability while driving heavy capacitive loads
is another key advantage over comparable CMOS rail-
to-rail op amps.
V
IN
V
IN
50mV/div
50mV/div
V
OUT
V
OUT
50mV/div
50mV/div
2/MAX495
10µs/div
10µs/div
Figure 7b. MAX492 Voltage Follower with 500pF Load—
Figure 6. MAX492 Voltage Follower with 1000pF Load
R
= 20kΩ
(R = ∞)
L
L
V
IN
V
IN
50mV/div
50mV/div
V
OUT
V
OUT
50mV/div
50mV/div
10µs/div
10µs/div
Figure 7a. MAX492 Voltage Follower with 500pF Load—
= 5kΩ
Figure 7c. MAX492 Voltage Follower with 500pF Load—
= ∞
R
R
L
L
12 ______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
