MAX4450-MAX4451 Maxim, MAX4450-MAX4451 Datasheet - Page 7

• Manufacturer Part Number: MAX4450-MAX4451
• Description: Ultra-Small / Low-Cost / 210MHz / Single-Supply Op Amps with Rail-to-Rail Outputs
• Manufacturer: Maxim

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
210MHz 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.
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 2.25V of the positive supply rail.
The MAX4450/MAX4451 are internally compensated for
unity gain. When configured for unity gain, the devices
require a 24Ω resistor (R
path. This resistor improves AC response by reducing
the Q of the parallel LC circuit formed by the parasitic
feedback capacitance and inductance.
MAX4450
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Ultra-Small, Low-Cost, 210MHz, Single-Supply
PIN
MAX4451
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Applications Information
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Detailed Description
Choosing Resistor Values
NAME
OUTA
OUTB
INA+
INB+
OUT
INA-
INB-
F
V
V
IN+
IN-
) in series with the feedback
CC
EE
Unity-Gain Configuration
Pin Description
Amplifier Output
Negative Power Supply
or Ground (in single-
supply operation)
Noninverting Input
Inverting Input
Positive Power Supply
Amplifier A Output
Amplifier A Inverting
Input
Amplifier A Noninverting
Input
Amplifier B Output
Amplifier B Inverting
Input
Amplifier B Noninverting
Input
Op Amps with Rail-to-Rail Outputs
FUNCTION
Select the gain-setting feedback (R
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-
verting gain-of-two configuration (R
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 200Ω 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.
These amplifiers operate from a single +4.5V to +11V
power supply or from dual ±2.25V to ±5.5V supplies. For
single-supply operation, bypass V
Figure 1a. Noninverting Gain Configuration
Figure 1b. Inverting Gain Configuration
R
IN
TIN
R
G
Layout and Power-Supply Bypassing
IN
R
R
TIN
G
Inverting and Noninverting Configurations
R
S
MAX445 _
MAX445 _
R
V
F
R
V
OUT
F
OUT
= -(R
= [1+ (R
F
/ R
F
G
) V
/ R
R
IN
TO
G
R
)] V
TO
CC
IN
F
F
= R
) and input (R
to ground with a
G
) using 1kΩ
V
OUT
V
OUT
R
O
R
G
O
7
)