MAX4309ESA MAXIM [Maxim Integrated Products], MAX4309ESA Datasheet - Page 9

• Manufacturer Part Number: MAX4309ESA
• Description: 400MHz, Ultra-Low-Distortion Op Amps
• Manufacturer: MAXIM [Maxim Integrated Products]

_____________________Pin Description
The MAX4108 is internally compensated for unity gain.
When configured for unity gain, the device requires a
small resistor in series with the feedback path. This
resistor improves the AC response by reducing the Q
of the tank circuit, which is formed by parasitic feed-
back inductance and capacitance.
Figure 1a. Using an Isolation Resistor for High Capacitive
Loads
_______________Detailed Description
PIN
4, 5
7, 8
1
2
3
6
NAME
N.C.
OUT
V
IN+
V
R
IN-
V
CC
G
EE
IN
MAX4108
MAX4109
MAX4308
MAX4309
PART
No Connection. Not internally connected.
Inverting Input
Noninverting Input
Negative Power Supply, connect to -5V
Amplifier Output
Positive Power Supply, connect to +5V
_______________________________________________________________________________________
400MHz, Ultra-Low-Distortion Op Amps
R
R
Choosing Resistor Values
F
F
500
500
500
24
( )
R
Unity-Gain Configuration
G
500
125
56
( )
FUNCTION
GAIN (V/V)
R
S
10
C
1
2
5
L
R
L
DC
DC
.
.
The values of the gain-setting feedback and input resis-
tors are important design considerations. Large resistor
values will increase voltage noise, and will interact with
the amplifier’s input and PC board capacitance to gen-
erate undesirable poles and zeros, which can decrease
bandwidth or cause oscillations. For example, a nonin-
verting gain of +2, using 1kΩ resistors combined with
2pF of input capacitance and 0.5pF of board capaci-
tance, will cause a feedback pole at 128MHz. If this
pole is within the anticipated amplifier bandwidth, it will
jeopardize stability. Reducing these 1kΩ resistors to
100Ω will extend the pole frequency to 1.28GHz, but
could limit output swing by adding 200Ω in parallel with
the amplifier’s load. Clearly, the selection of resistor val-
ues must be tailored to the specific application.
The MAX4108/MAX4109/MAX4308/MAX4309 are ultra-
low-distortion, high-bandwidth op amps. The output
distortion will be degraded as the total load resistance
seen by the amplifier decreases. To minimize distortion
products, keep the input and gain-setting resistors rela-
tively large. A 500Ω feedback resistor combined with
an appropriate input resistor to set the gain will provide
excellent AC performance without significantly increas-
ing distortion.
Figure 1b. Optimal Isolation Resistor (R
Inverting and Noninverting Configurations
25
20
15
10
5
0
10
MAX4308
40
MAX4109/MAX4309
70
CAPACITANCE (pF)
100
MAX4108
130
160
S
) vs. Capacitive Load
190
220
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