MAX4490 Maxim, MAX4490 Datasheet - Page 7

• Manufacturer Part Number: MAX4490
• Description: The MAX4490/MAX4491/MAX4492 single/dual/quad, low-cost CMOS op amps feature rail-to-rail input and output capability from either a single +2
• Manufacturer: Maxim

In conjunction with op amp output resistance, capaci-
tive loads introduce a pole frequency that can reduce
phase margin and lead to unstable operation. The
MAX4490/MAX4491/MAX4492 drive capacitive loads
up to 300pF without significant degradation of step
response and slew rate (Figure 4). Capacitive-Load
Stability (page 1) shows regions of stable and margin-
ally stable (step overshoot <10%) operation for different
combinations of capacitive and resistive loads.
Figure 3. Step Response With and Without Feedback
Compensation
3a)
3b)
A
A
V
V
= -1, R
= -1, R
WITHOUT FEEDBACK COMPENSATION
WITH FEEDBACK COMPENSATION
_______________________________________________________________________________________
L
L
= 4kΩ, C
= 4kΩ, C
Driving Capacitive Loads
f
f
= 5pF
= 0
Rail-to-Rail I/O Op Amps in SC70
Low-Cost, High-Slew-Rate,
Improve stability for large capacitive loads by adding
an isolation resistor (typically 10Ω) in series with the
output (Figure 5). Note that the isolation resistor forms a
voltage divider with potential for gain error.
MAX4490 TRANSISTOR COUNT: 60
MAX4491 TRANSISTOR COUNT: 120
MAX4492 TRANSISTOR COUNT: 240
SUBSTRATE CONNECTED TO V
Figure 4. Step Response With and Without Capacitive Loading
4a)
4b)
A
A
V
V
= +1, R
= +1, R
WITHOUT CAPACITIVE LOADING
L
L
= 100kΩ, C
WITH CAPACITIVE LOADING
= 100kΩ, C
L
L
= 0
= 300pF
Chip Information
SS
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