MAX4452/MAX4453/MAX4454/MAX4352/MAX4353/MAX4354
Low-Cost, +3V/+5V, 620µA, 200MHz,
Single-Supply Op Amps with Rail-to-Rail Outputs
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Detailed Description
The MAX4452/MAX4352 single, MAX4453/MAX4353
dual, and MAX4454/MAX4354 quad, single-supply, rail-
to-rail, voltage-feedback amplifiers achieve high slew
rates and wide bandwidths while consuming only
620µA per amplifier. Excellent speed/power ratio
makes them ideal for portable devices and high-fre-
quency signal applications.
Internal feedback around the output stage ensures low
open-loop output impedance, reducing gain sensitivity
to load variations. This feedback also produces
demand-driven current bias to the output transistors.
Rail-to-Rail Outputs, Ground-Sensing Input
The input common-mode range extends from (V
EE
-
0.1V) to (V
CC
- 1.5V) with excellent common-mode
rejection. Beyond this range, the amplifier output is a
nonlinear function of the input, but does not undergo
phase reversal or latchup.
The output swings to within 180mV of either power-sup-
ply rail with a 1kΩ load. The input ground-sensing and
the rail-to-rail output substantially increase the dynamic
range.
Output Capacitive Loading and Stability
The MAX4452/MAX4453/MAX4454/MAX4352/MAX4353/
MAX4354 are optimized for AC performance. They are
not designed to drive highly reactive loads. Such loads
decrease phase margin and may produce excessive
ringing and oscillation. The use of an isolation resistor
eliminates this problem (Figure 1). Figure 2 is a graph
of the Optimal Isolation Resistor (R
ISO
) vs. Capacitive
Load.
Applications Information
Choosing Resistor Values
Unity-Gain Configuration
The MAX4452/MAX4453/MAX4454 are internally com-
pensated for unity gain. When configured for unity gain,
a 24Ω feedback resistor (R
F
) is recommended. This
resistor improves AC response by reducing the Q of
the parallel LC circuit formed by the parasitic feedback
capacitance and inductance.
Inverting and Noninverting Configurations
Select the gain-setting feedback (R
F
) and input (R
G
)
resistor values that best fit the application. Large resis-
tor values increase voltage noise and interact with the
amplifier’s input and PC board capacitance. This can
generate undesirable poles and zeros and decrease
bandwidth or cause oscillations. For example, a nonin-
verting gain-of-two configuration (R
F
= R
G
) using 1kΩ
resistors, combined with 2pF of amplifier input capaci-
tance and 1pF of PC board capacitance, causes a pole
at 106MHz. Since this pole is within the amplifier band-
width, it jeopardizes stability. Reducing the 1kΩ resis-
tors to 100Ω extends the pole frequency to 1.06GHz,
but could limit output swing by adding 200Ω in parallel
with the amplifier’s load resistor.
Note: For high-gain applications where output offset
voltage is a consideration, choose RS to be equal to
the parallel combination of RF and RG (Figures 3a and
3b).
3b):
vs. CAPACITIVE LOAD
