Ultra-Small, Low-Cost, 210MHz, Single-Supply
Op Amps with Rail-to-Rail Outputs
Inverting and Noninverting Configurations
Pin Description
Select the gain-setting feedback (R ) and input (R )
F
G
resistor values to fit your application. Large resistor val-
ues increase voltage noise and interact with the amplifi-
er’s input and PC board capacitance. This can
generate undesirable poles and zeros and decrease
bandwidth or cause oscillations. For example, a nonin-
PIN
NAME
FUNCTION
MAX4450 MAX4451
1
—
OUT
Amplifier Output
Negative Power Supply
or Ground (in single-
supply operation)
verting gain-of-two configuration (R = R ) using 1kΩ
F
G
±
4
V
EE
resistors, combined with 1pF of amplifier input capaci-
tance and 1pF of PC board capacitance, causes a pole
at 159MHz. Since this pole is within the amplifier band-
width, it jeopardizes stability. Reducing the 1kΩ resis-
tors to 100Ω extends the pole frequency to 1.59GHz,
but could limit output swing by adding ±00Ω in parallel
with the amplifier’s load resistor. Table 1 lists suggest-
ed feedback and gain resistors, and bandwidths for
several gain values in the configurations shown in
Figures 1a and 1b.
3
4
—
—
8
IN+
IN-
Noninverting Input
Inverting Input
5
V
Positive Power Supply
Amplifier A Output
CC
—
1
OUTA
Amplifier A Inverting
Input
—
±
INA-
Amplifier A Noninverting
Input
—
—
—
3
7
6
INA+
OUTB
INB-
Layout and Power-Supply Bypassing
These amplifiers operate from a single +4.5V to +11V
power supply or from dual ±±.±5V to ±5.5V supplies. For
Amplifier B Output
Amplifier B Inverting
Input
single-supply operation, bypass V
to ground with a
CC
Amplifier B Noninverting
Input
—
5
INB+
R
R
F
G
Detailed Description
The MAX4450/MAX4451 are single-supply, rail-to-rail,
voltage-feedback amplifiers that employ current-feed-
back techniques to achieve 485V/µs slew rates and
±10MHz bandwidths. Excellent harmonic distortion and
differential gain/phase performance make these ampli-
fiers an ideal choice for a wide variety of video and RF
signal-processing applications.
R
TO
V
OUT
MAX445 _
IN
R
O
V
= [1+ (R / R )] V
F G
OUT
IN
R
TIN
The output voltage swings to within 55mV of each sup-
ply rail. Local feedback around the output stage
ensures low open-loop output impedance to reduce
gain sensitivity to load variations. The input stage per-
mits common-mode voltages beyond the negative sup-
ply and to within ±.±5V of the positive supply rail.
Figure 1a. Noninverting Gain Configuration
R
R
F
G
IN
Applications Information
R
TIN
R
TO
V
OUT
Choosing Resistor Values
MAX445 _
Unity-Gain Configuration
The MAX4450/MAX4451 are internally compensated for
unity gain. When configured for unity gain, the devices
R
O
V
= -(R / R ) V
F G
OUT
IN
R
S
require a ±4Ω resistor (R ) in series with the feedback
F
path. This resistor improves AC response by reducing
the Q of the parallel LC circuit formed by the parasitic
feedback capacitance and inductance.
Figure 1b. Inverting Gain Configuration
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7
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