MAX4321 View Datasheet(PDF) - Maxim Integrated
Part Name
Description
Manufacturer
MAX4321 Datasheet PDF : 12 Pages
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Low-Cost, Low-Voltage, Rail-to-Rail,
Input/Output, SOT23 5MHz Op Amp
Rail-to-Rail Output Stage
The minimum output voltage will be within millivolts of
ground for single-supply operation where the load is
referenced to ground (VEE). Figure 3 shows the input
voltage range and output voltage swing of a MAX4321
connected as a voltage follower. With a +3V supply
and the 100kΩ load tied to ground, the output swings
from 0.02V to 2.97V. The maximum output voltage
swing depends on the load but will be within 300mV of
a +5V supply, even with the maximum load (250Ω to
ground).
Driving a capacitive load can cause instability in most
high-speed op amps, especially those with low quies-
cent current. The MAX4321 has a high tolerance for
capacitive loads. It is stable with capacitive loads up to
500pF. Figure 4 gives the stable operating region for
capacitive loads. Figures 5 and 6 show the response
with capacitive loads and the results of adding an isola-
tion resistor in series with the output (Figure 7). The
resistor improves the circuit’s phase margin by isolating
the load capacitor from the op amp’s output.
VCC = 3V
IN AV = +1
OUT
2µs/div
RL = 100kΩ
Figure 3. Rail-to-Rail Input /Output Voltage Range
AV = +1
CL = 500pF
IN
10,000
1000
UNSTABLE
REGION
RL TO VEE
VOUT = VCC / 2
100
100
1k
10k
100k
RESISTIVE LOAD (Ω)
Figure 4. Capacitive-Load Stability
AV = +1
CL = 1000pF
IN RS = 39Ω
OUT
400ns/div
Figure 5. Small-Signal Transient Response with Capacitive
Load
OUT
400ns/div
Figure 6. Transient Response to Capacitive Load with Isolation
Resistor
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