Datasheet

Detailed Description
The MAX4350/MAX4351 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 125mV 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.
Applications Information
Choosing Resistor Values
Unity-Gain Configuration
The MAX4350/MAX4351 are internally compensated for
unity gain. When configured for unity gain, a 24Ω resis-
tor (R
F
) in series with the feedback path optimizes AC
performance. 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 to fit your application (Figures 1a and
1b). Large resistor values increase voltage noise and
interact with the amplifier’s input and PC board capaci-
tance. This can generate undesirable poles and zeros
and decrease bandwidth or cause oscillations. For
example, a noninverting gain-of-two configuration (R
F
=
R
G
) using 1kΩ resistors, combined with 1pF of amplifier
input capacitance and 1pF of PC board capacitance,
causes a pole at 159MHz. Since this pole is within the
amplifier bandwidth, it jeopardizes stability. Reducing
the 1kΩ resistors 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.
Layout and Power-Supply Bypassing
These amplifiers operate from dual ±5V supplies. Bypass
each supply with a 0.1µF capacitor to ground.
Maxim recommends using microstrip and stripline tech-
niques to obtain full bandwidth. To ensure that the PC
board does not degrade the amplifier’s performance,
design it for a frequency greater than 1GHz. Pay care-
MAX4350/MAX4351
Ultra-Small, Low-Cost, 210MHz, Dual-Supply
Op Amps with Rail-to-Rail Outputs
_______________________________________________________________________________________ 7
Pin Description
PIN
OUT
V
EE
IN+
INA-
OUTA
V
CC
IN-
INB+
INB-
OUTB
INA+
—
4
—
2
1
8
—
5
6
7
3
1 Amplifier Output
2
Negative Power Supply
or Ground (in single-
supply operation)
3 Noninverting Input
—
Amplifier A Inverting
Input
— Amplifier A Output
5 Positive Power Supply
4 Inverting Input
—
Amplifier B Noninverting
Input
—
Amplifier B Inverting
Input
— Amplifier B Output
—
Amplifier A Noninverting
Input
IN
R
G
R
F
R
TO
R
TIN
R
O
OUT
MAX435 _
Figure 1a. Noninverting Gain Configuration
IN
R
G
R
F
R
TO
R
S
R
TIN
R
O
OUT
MAX435 _
Figure 1b. Inverting Gain Configuration
FUNCTION
MAX4350
NAME
MAX4351